Why is it not possible? Why is it not possible to create new starbase types? To limit what can be modified is not supporting mods really. Why have part of your code hard coded and part of it in xml files? Would seem to me to be easier with it totally one way or the other.
The starbases for example, if I wanted to be able to create a morale starbase to go with the existing 3 now, why shouldn't I be able to by adding it to a GC2SBtypes.xml (or so) and set modules to alter stats for the morale of planets within range, the abilities are already set up and named, but you can not access them.
Problems like the extreme changes you made to the economy should be in a mod file(s) as well. To force people to use *your* idea on what is right and wrong is ...well... not really morale now is it? What makes a good game great is replayability, and replayability is based on game play being altered to the point where seldom can you say 'been there, done that'.
Give us options please, not hardcode, economy options should be in sliders in the game menu, sort of like the star abundunt/rare choices, economy low/high, morale low/high, that sort of thing.