1) I can agree in principle. WIllythemailboy pointed out that supposedly the constructor spam and such will be reduced, but he neglected to give any indication of how, or cite the article where it was seen. In any case, reusable ships that have to be "reloaded" for each use of each appropriate module, would seem to be the best course.
2) This too I can agree with in principle, but not all economic systems are created equal. There are, at the ultimate core, only three different systemic economic foundations to choose from. Capitalism, in which the market is an unrefined and largely antisocial Darwinian model. Communism, in which either the Government (totalitarian) or the actual People (democratic) share equal ownership of all resources (or stewardship, as I call it). And finally, Piracy, in which a kind of formalized theft is the basis for a given organization's financial acquisitions.
An economic victory for any variant of capitalism is not going to be at all the same as that of a communist system, and either will be drastically far removed in implementation or scope from piracy. Anything less is just...the same economic systems in different skins, no matter the race.
While capitalism and communism (while poorly understood by many) are relatively common and known, piracy as a foundation for a national economy is not. Think of Germany circa 1940, or really any incarnation of the original Roman Empire, or any of the barbarian hordes such as the Huns, or the Vikings.
I think the best implementation of piracy would be specialized modules for those races who use piracy, as well as specialized star base modules and planetary improvements for that purpose. Using a copy of the influence mechanic as the basis, instead calculate the value of the loot by the capabilities of the vessel/star base/planet. What would constitute an economic victory for them, would be an end tech, (probably for a ship module) that would allow for "circular piracy" in which theft occurs in a never-ending loop so that the system becomes sustainable (which is its ultimate failing). This advancement is what would make it possible for a piracy-based nation to build up enough economic clout to potentially financially outstrip the other nations without actually having to conquer them all.
Obviously, the best implementation of capitalism would be the aforementioned Galactic Reserve Bank, though it would merely be a planetary improvement that does the same thing as the piracy ship module, because that's all it really is.
Communism would have some form of improvement or whatnot that would make money "meaningless" a la Star Trek's United Federation of Planets. It would be a facility that changes their economy so that all resources count as a large percentage of food, industry, ect. and nothing else. Basically, food and industry would simply directly count as money after the research of that tech.
Probably these facilities and modules would have incremental prerequisites that do the same things to lesser degrees, while the ultimate techs finally jack it to the max (which may be bad phrasing...but whatever).
3) This, I've been advocating for a very long time. I think the volume ("space", in the Gal Civ games) requirement of ships is sufficient to keep distinctions between "classes" of ships. Power Converter (there's really no such thing as a generator, because power is never "made" only transformed) stats would scale with the size of the hull. You could put more than one on, but they should take up a lot of volume (signifying the fuel they have to carry to operate, though it's otherwise not tracked as a resource), and more advanced techs would take up less volume while providing more power.
Modules such as weapons, defenses, engines, and special devices such as fleet modules and piracy modules, would have power ratings that detract from the converter's output. It would become a balance of capability, volume, and power. I think that would dovetail nicely with the Devs' admitted interest in incorporating combat roles into fleet composition. And it would remain relatively simple to implement.
Again, someone else already implied the Devs have mentioned that they intend to incorporate modules that enhance weapons and defenses and the like in specific ways, rather than the simple general attack and defense boosts of Gal Civ II. This would make sense since they did mention in Q&A #1 (see how I cited where I saw that?) that they would like to include aspects such as weapon range into combat with Gal Civ III. But again, they didn't mention where they saw it. This too though, I've been advocating for a while, and again I think it would go well with their intent to incorporate specialized combat roles.
4) It would be nice, but it's not going to happen, sadly. Though I'll admit, I don't find it lacking on the part of the game. It would be an addition, not the inclusion of a missing component.
5) I can agree to this, mostly. But there needs to be some way of adjusting how cooperative they are by how much they like you. Just because you're allies, doesn't necessarily mean they'll do what's in your best interest. To use your own example, if your ally really liked you, they'd do exactly as you specify, essentially. If they weren't very fond of you but simply hated your mutual enemy enough to ally with you, then odds are they'll blow you off and do as they please whether it's a good idea or not (depends on how smart the AI is). Not sure how they'd go about that, but I think it's worth looking into.
I also very much agree that allied fleets should be able to occupy the same hexes, and that allied fleets should be able to orbit ally's worlds and defend them as such. I don't think it's reasonably possible to merge allied fleets into one though. But if it is, the ally with the greatest military rating should control it...which may not always be the player.
6) This I think needs to be tabled until we get a better idea of how these new Ideologies are going to work. Otherwise, I mostly agree with what you say here.
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(Now it's my turn)
7) Mines. Oh Noes! Not mines! Yes, mines. As many have pointed out, space is simply too big to make minefields effective. Good to know...because space is too big to make space battles effective, either. The only space warfare you'll ever see in reality is orbital bombardment and invasion. There is no minefield, fleet, or other form of mobile or stationary defensive perimeter, that another fleet can't simply go around. But, that's not fun, and it's not necessarily universally true, either. But ultimately, in the context of this game, that's all irrelevant.
As someone else pointed out, this is a 2D game, not a 3D one. As such, space is a fraction of the size in the game that it is in reality. Additionally, the scale of space in the game is radically different from that of reality. If each hex represented 1 AU, a gigantic map would only ever have one star on it. As such, a given hex must be at least 1 light-year, since one parsec is much too large (it would mean any given planet is 3 light-years away from its star). That's still kind of absurd though. How about we go with MAU (Mega Astronomical Units)? At that point, one parsec would be 20 hexes so star systems would still be much too close together on maps, but at least star systems wouldn't be quite as cartoonishly overinflated. Frankly, the scaling of the game simply doesn't realistically work, period. It's intended solely as a visual abstraction of the concept of interstellar and interplanetary distances.
At that point, in a 2D plane, filling a hex with mines isn't infeasible. And since we're already using up way more resources in the game than could possibly exist in any star system or hundreds of star systems, filling the hexes surrounding a star system with mines really isn't a stretch. Give a hex-worth of mines a comparable production and maintenance cost to a medium-size ship of the appropriate tech level, and voila...mines that are useful, but not easy to spam. Different races could use mines in different ways. Some might have dummy mines that just mostly sit inert and magnetically drift toward targets, while others might have mines that are more like automated drones that fly through space and kamikaze trespassers. That's mostly all a matter of detail. But in terms of game function, it's reasonable, and it works without disrupting balance. The ultimate tech of course would be self-propelled mines that hang around asteroid fields and are equipped with 3D printers to make more of themselves.
A nuke or other EMP weapon may disable or detonate mines, but it will be slow, and uncertain unless you know there's a minefield there. Which in space, is unlikely. Radar as a technology is largely already topping out on both sides...detection and stealth. Radio waves just don't do that much. Other sensors will do more, but will still eventually top out. At a certain point, it becomes guesswork no matter what. So...nuking a minefield works, but it's hardly a "counter" to them. Also, if they become solid-state optronic systems, EMPs become meaningless, and only destroying them does any good.
8) Hyperspace inhibitors and different drive mechanisms. Any device that can be made to alter space to allow ships to cheat relativity, can be further made to force those ships out of that altered space. This creates the kind of bottlenecking that makes minefields and fleets actually effective in the vastness of space. It also means that covert operations become much more valuable to try and circumvent such defenses.
Inhibitor tech would come in two forms, planetary improvements/star base modules that reduce all ship (including friendlies) speeds by so many spaces/turn (with the max tech dropping it all the way to 1), and single-purpose mini-bases that create a straight corridor through which inhibitor effects (even those from multiple sources) of equal or lesser tech level are completely nullified. Facilitators of lesser level than inhibitors would have no effect. Thus, you'd have two ways to bottleneck opponents. Build bases far enough apart to leave small gaps to travel through, or overlap everything and use the facilitators to make corridors through those zones.
I also think it would be more interesting to see different races having adapted their understanding of the gate/hyperdrive relationship in unique ways. The Drengin and Arceans (gone now) would likely have projectors that function more like gates than the hyperdrives. Just like the old Arcean improvement in GCII that sped up their ships because they were otherwise slower than molasses in winter. Have planetary improvements and star base modules that improve ship movement speed within their respective ranges, but no ship modules affecting speed. It gives the Drengin more incentive to militarize their space, and keeps them a real threat without forcing everyone into the "land rush" that was predominant in GCII. This would also go well with their piracy economic system (c'mon, of course they're going to be like vikings, attacking and plundering others instead of working themselves), as their abundance of star bases would expand their capacity to raid other worlds as well.
Other races could adapt the hyperdrive tech to their less in-depth understanding and more limited power capabilities by outfitting a single ship with one large field generator, and little else. All ships in a fleet with that ship, would travel at the "jumpship's" listed speed. Any non-jump-capable craft would travel at a speed of 1, otherwise.
Then of course you'd have the normal drives that have been used throughout GC. Nothing really needs to be said on them except that they should look less like rocket engines and more like field generators of some kind...or at least components that would contain such generators.
9) The Terrans should have better power plants than any other race. The justification for Terrans figuring out hyperdrive is that they're more creative, and could meet the drastic power requirements of such drives with their abundance of fusion power. If power was that much of a problem for the other races, so easily solved by a race so young, then the power plants of the Terrans must be an order of magnitude better than everyone else's. This should be at least partially reflected in either the volume of their ships (an increased ability to support weapons, defenses, and engines), or in power modules with greater capacities compared to other races' plants of identical volumes (assuming power modules were included later in development).
10) Someone mentioned the idea of flagships. I like this idea. I think it would best be implemented by a module, with minimal power and volume cost, but extremely high production and maintenance cost, that is unique and can only be outfitted on one ship at a time. It would designate that vessel the empire's flagship, and confer various bonuses (unique to each race) to its fleet and/or the planet it's orbiting, or all ships within a certain range and/or all worlds within that range, or all ships everywhere in the navy and/or all worlds in the empire.
That is all.