The "Fixed-Income Game", or "Galactic Domination on $10 a Day", sounds interesting. As an added twist make space yard build rates insanely high. That would force players to really prioritize their building throughout their empire.
For the "Half-Life game" fighters would rule and the AS would be hated! Hell, take out the self-destruct device and watch the fun as everyone tries to steal each others ships!
Either one (or both) of these games would be a fun change of pace.