I could definitely incorporate the arena concept into it, but it would expand outwardly for peole that want it to and as i'm writing this my head is suddenly swimming with how to make it work more feasibly.
HP becomes exhaustion. One die describes the action, the other describes how much 'damage' it does and posts are written accordingly. And i think d20 is better.
i,e, suck 20 is pretty much 'finish the job' and suck 1 would be something out of netspeak cybersex.