Somebody must have requested this game format before but if not....

  Come on, how fun would it be to control EVERY race in your family!  Set up with 20-30 families (players)
and allow them to best combine their empire's resourses and power. 

Anouther Idea:   Pirates!  Have new "combat units" that are mercs so you can attack allies and even family members with only a small chance of being discovered.  I know the came is about cooperation to kick the other guy but how many families are all lovie-dovie?  The penalty besides retaliation from the offended could be some economic sacctions or a few inactive turn penalties with the annoucement of the treachery to the rest of the galaxy.