[warbiscuit]

That's pretty much exactly how the EtherDelta smart contract works. The contract can only move coins you've signed an order for, and only when it's properly paired with a matching counter-order.

I think the mainly catch would be scaling the speed (etherdelta is limited to the ETH network block rate). I don't know too much about lightning's details, but given that they've demonstrated atomic cross-chain swaps, I bet it's set up to handle something exactly like what's needed.

Which is quite exciting... I just always moderate my enthusiasm because for all complex software projects, the devil (and 80% of the work) is in the details :)