Ok lets get this ball rolling. Will be updating.
Constructors- They don't get used on on building Stations, but they have a few turns of cooldown ie resupply and get ready for the next project. You can link constructors to stations. Stations auto upgrade their stats over time slowly and they will need constructors only to make this process go faster and to upgrade to the next level. (will spill more details below)
Military- (this has a 3-5 levels of size). early on few weapons, light repair ability, small hangar/warehouses ie range support for the empire and small sensors. Later on more weapons become available, better sensor package, more repair, they can start buffing nearby fleets, more armor, improves planetary ship production capability, they can increase fleet size of near by fleets, they can manage wormholes and make them stable (think Babylon 5), high end upgrades can protect 1-3 planets near them from invasion so you have to go through the military station first, with better sensor pages they can reveal hidden goodies and better protection against randoms/ random events. Can be built anywhere.
Mining- Only one level. Auto upgrades with better mining, small support range bonus, small bonuses to getting worlds up and running, habitat modules and light sensor package. No weapons ie civilian station it doesn't want the enemies attention. Can only be built in your space.
Diplomatic/Influence- (3 Levels) They can help spread your influence, build embassies for certain empire to establish relationships and help with espionage, tapping into galactic info nets, small econ/trade bonuses, small sensor package, small support range bonus, helps bring aliens to your worlds ie habitat modules, and flipping enemy worlds to your side. No weapons ie civilian station it doesn't want the enemies attention. Buildable anywhere.
Trade- (3 Levels) They support getting worlds up and running, boost econ and trade, more trade routes, placing where other empires trade routes are coming through relations bonus, social production bonuses, small sensor package, small support range bonus, small morale bonus ie investing in the empire, and habitat modules. No weapons ie civilian station it doesn't want the enemies attention. Only buildable in your space.
Good for now.