Hey Jay, I'm madly, madly in love with this game. I'm sure people have had similar ideas to these in the past, but have you considered some sort of tech level-gated 'unlocks'? I've been thinking about different carrier types. Each would cost more than a regular carrier... $100 each?
Scanning 10 could unlock Stealth Carriers that halve the range they show up on enemy scanners.
Range 10 could unlock Warp Carriers that move between any system at 2x speed, and combine with warpgates to move at 4x speed.
Weapons 10 could unlock Gunship Carriers that add an extra 1-2 levels of weapons tech in fights.
Banking 10 could be Trade Fleets- a shipless carrier that you send to other players... it gives them some amount of free money then becomes their Trade Fleet. Then, hopefully, they send it back to you for the same bonus and so on.
Thanks for an amazing game!! Keep up the fantastic work!