1. Its obvious that at some point they will will all group into a fighting orgy even if the map is large + messy camerafix 1. large maps, small wont work for obvious reasons.
2. rendering, on teh wiiU it shouldnt be a big issue. as far as rendering is consorned id expect around 10 on the normal wii, and its graphcis could pass as xbox. only issues i see would be from playabililty or issues in the playlist.
2. Nobody wants to play smash bros with bad graphics and low FPS, sacrifacing those aspects instead of maximum georgeous 4player action just to play 15 player online is not worth it.