A fun setting could be to have every settlement owned by randomly generated factions. The player starts with two 20/20 armies and 0 settlements. the victory condition would be to capture 200 settlements. Like the UCV (ultimate campaign victory) you would spawn near the capital of the faction you choose and can choose to take it or the surrounding area. you would not receive attrition from loss of supply line till after the 2nd round.
I think it sounds like fun but maybe I'm alone on that. Let me know what you all think.