I probably won't have time to play for a while, but I hope this is food for thought:
To take an example, PaC for semi-competitive play.
For asymmertic Abraxis-and-Creeper, this is relatively straightforward if a) the players are equipped with different buildable units, and b) the host plays the Creeper side. It will probably need GetOwner [UID - int]. (NB: This can still be co-op if the Creeper units are friendly.)
For symmetric Creeper-and-Creeper, it becomes more complex, but adding SetOwner would handle most things.