Nothing to do with SSB, Z... It's just a simple Free for All... Or "Battle Royale", as some like to call it.
Though, I agree with Seno. Personally, I've never done a battle RP with more than one person. I think it'd turn out rather disasterous.
"Round Robin" works for an odd number... where as a continuing Bracket Style would work best for an even number, I expect.
Either way, though... These style RP battles tend to take too long to determine a 'victor'. If we have too many people, it may be AGES before we come up with a 'winner' to this tournament bit.