This is a scn i made ages ago that I've got alot of good feedback from and is probably one of my best scns.
First round is FFA in the bottom left hand corner...once all units are dead apart from the nation whos last standing it moves onto round 2 where its 2v2 cit wars and after that is FFA again with rocketbases in the middle but protected with neutral AA guns and towers which when destroyed will let you fire rockets at anyone.
Its all explained in the objectives in the scn enjoy =).