First, category names. I'd suggest:
- throneships => if the factions are "noble" types, that could fit. Idea there would be that each "house", or background faction, would compete to make the shiniest and most op one.
- simply... battleships.
Next, OP is possible ?
Phantom projector => constantly creates 1hp doubles of your ships.
Parasitic worm => Could take over a dire guardian.
Transport teleport.
Mortar ship => once an hour (maybe less ?) ship that can target stuff on another planet in the same solar system.
Resurrector ship => same as the golem really, but... a ship.
=> Basically a toned-down version of all golems could fit. I'm writing that with the last 2 ships...
Attritionist => has the attrition capability.
Hubble => Scout shisp that scouts the solar systems adjacent to the solar system where it's in.
I don't actually see why this should limit the player to ships though, so... buildings ?
- lost fleet anchor (attracts fleets of low-tech ship once in a while, with a different cap)
- Marauder bar (same idea but the fleet would be people that lost their ships in the bar, would generates less ships, but in compensation would bring income from drinks).
- Advanced mineral extraction => these guys have figured out how to get even the tiniest traces of metal in asteroids, boosting your generation of metal by XX%.
- Mercenary docks (where you could... hire mercs. A bit (lot) less expansive that in AI war 2. Possibly could also hire a group of mercs to patrol your territory like zombies. Them being hostile and targetting other systems seems too complicated but could be cool.
- "Cap modifiers" (needs a name tied to the ship type), like "Advanced fighter control center" => doubles the cap of fighters, gives them an upgrade too.
- Neinzul fountain of youth => halves the life degeneration of neinzuls.
- Space whale nest. This place happens to be the home of an old hydra space-faring pet, that looks like whales. Those are transport that can regenerate, but need to go back to the nest once in a while. Number of transport available, if dead, regenerate with time (to simulate reproduction of the "animals" there).
That's all I can think of for the moment...
PS: in case trains make it in the game, spy train.
PS2: added neinzul founain, cap modifier, attritionist, hubble.
PS3: space whales.