Can the player get an alarm "module"?
Isn't this an option under CTRLS => Planet-specific options? Alert if > X ships present?
On ship platforms:
In AI War classic, the human player generally has a lot fiddlier defense setups than the AI. That's fair because you're countering much larger numbers, and because the AI doesn't need to understand the human defenses to throw gobs of ships at them.
When attacking a guard post or fortress, though, you're usually dealing with just one structure that frequently has an obvious triangle counter. Put two together (fortress or FF on top of a guard post), and now you might not have a triangle counter, but perhaps there's a bonus ship that would be perfect if you had it. Or perhaps not, a post that wrecks polycrystal next to a fortress is just going to be painful.
Are mod fort command stations interesting to kill as a player? Or are they just a pain to kill no matter what you do? Because a pile of random modules can mean there isn't really any counter.
So, I'm worried that AI platforms could become very hard for a player to read and not particularly counterable. Either they should have very few modules, or the logic for picking AI modules should be careful to create platforms with enough personality to be counterable.
Overall, I think the city-building aspect of human space platforms might be a rabbit-hole of complexity. I'm all for abstractions to streamline setting up defenses, but staying at a pretty high level of abstraction might be fine here.
This does also sound suspiciously like modules.
Oh, and swapping engines onto a platform temporarily to reposition it and then swapping back to an all-offensive loadout sounds like a recipe for annoying micro. Platforms should be able to move to allow repositioning, but moving should disable their attacks; an engine module might make them able to move and shoot (roll your own Sentinel Guard Post).
I was more expecting space platforms to be MOSTLY about the core, and then have a very small number of support slots. Each slot can get a FF module or a range boost module or a damage boost module. Gravity/tractor/tachyon could be support modules on regular turrets or be options on a special support-turret platform. This is probably also a rabbit hole, but it's not nearly as deep. I think it's roughly equivalent to replacing human turrets with Mod Forts.
Or just have variants (like for ships) that either have a support part or don't. IE, this is a lightning turret platform, and it comes in regular or FF protected flavors. Pick one. I feel like for most turret types, and really most defensive structures, it's pretty clear whether or not you want FF coverage, though you don't have enough FFs to cover all the turrets you'd like to.