I like option 1, too. Total decentralization is like the holy grail of online poker, but it seems to me that a central server would still be needed to organize the games, keep them moving along at a reasonable pace, and to act as a trusted escrow service to transfer funds back and forth. Maybe you could build a p2p client to handle all that, but then you'd get cheaters building their own clients to get around any constraints.

It's an interesting problem anyway and I'm pretty sure there is a big market for it. My own informal survey of bitcoin gaming sites tells me that the most profitable sites are also the 'provably fair' sites (bitZino, Just-Dice, etc). People aren't fools (for the most part). A provably fair HU poker site would almost certainly get a lot of action from high-rollers ... is my guess. I can see the $$ in their eyeballs now.