This is just a random idea that popped into my head. Basically, there would be a handful of territories, like in Risk, but each territory would be a particular map. The clan leaders would place their armies on the different territories, and when attacking, instead of rolling dice, they'd play a single match on the map. Instead of rolling 2 dice vs. 1 or whatever if it was two armies vs 1, one team would actually play with twice as many people -- so 8 vs 4 or something like that.
Just a thought. Could be fun, though.