I used to think that there needed to be different rules for space stations, but not these days.  For the purposes of starmada, the game is all based on the ship's/station's ability to destroy the opposing fleet - for that we have VPs.  If you make a station have 1.5x of the hull spaces, you still have to 'pay' for it in VPs.

What make space stations needed are in campaigns.  Most of my non-mobile ships (stations) are not firing platforms, but manufacturing facilities and if I have allowed my enemy's fleets get to those, I'm screwed...

-Bren