I think it might work if it is optional and doesn't replace any arenas, otherwise some people will be PO'd. I personally would like to see arenas that will allow more players like mabey 400, something like that, to keep the teams pretty even, if you have 12 people, then even one player joining could tilt the tide of the war as it will allow their team to cover more ground, while if you have 50 people, the teams can't be even anyway but the numbers make it so it is not that big of an advantage, and 5 people join it is still not that big of an advantage, they might shoot down a couple more transports or kill a few more tanks, but still not that big a deal, same principle