I think it could be a good idea but only if all participants would be forced to stay in their chosen faction when the event begins. If players could switch to a different faction whenever they wanted then there wouldn't be much difference than how faction rep is currently earned. There would also be disputes as to which faction wins if all players represented all factions, which would defeat the whole point of having the event. (I'm kind of drunk at the moment but did that make sense to anybody?)