Hmm.. I tried to make a 2 vs 2 game in skirmish.. Homever, I have a little problem.
I put paranoid on "yes" and made some triggers. Homever, the "paranoid" tag makes the computer declare war against me just after the alliance trigger has ran.
I tried making an another trigger that makes the computer ally with me after 50 secs of gameplay, but the trigger doesn't do anything (again, Paranoid's fault?)
And, when the computer declares war on me, I'm still allied with the computer, although the computer isn't allied with me.
Btw, I found some houses named Multi-Player 0, Multi-Player 1, Multi-Player 2 etc. from FinalSun. I tried making those ally with eachother, but after I closed the Tigger editor and opened it again the house names were changed to GDI (Multi-Player 0), Nod (Multi-Player 1), Neutral (Multi-Player 2) and Special. (Multi-Player 3)
Haven't tried making Multi-Player 4, Multi-Player 5, Multi-Player 6 and Multi-Player 7 ally with eachother yet.
EDIT: Tried to make GDI ally with Multi-Player 4, and it crashed after a few seconds of gameplay. So, it doesn't seem to work