general modding question

[Suicide Junkie]

Other than the ones already defined, no.
You could merge Lifesupport & crew quarters, then use the freed-up requirement to do reactors.

OR, you can merely make reactors useful to put on ships, so that players "have to" design them in.
By this, try replacing "supply storage" with "reactor power".
Give your reactors "solar supply generation" plus "supply storage".
Each reactor will then allow your ship to do only so many things per turn.
In order to design a transport, one reactor is enough. To build a BattleCruiser capable of firing its wavemotion gun 10 times per game turn, you'd need 10 transport reactors, or one giant battle reactor.