Am all for p2p platforms, and quite pleased to see more and more developing even as giant centralised exchanges seem to still take centre stage. I would make Bitcoin your core pair, however. From what I can see in your post, SBD is the currency you'll start to use, but when even Dan Larimer seems to be getting royally pissed with his own abomination (though abandoning it for yet another abomination of his creation tells me he's just moving on for bigger and better cows to milk) you might want to anchor your platform to the only cryptocurrency worth trading with long term.

Your post doesn't seem to address at all the security issue though. Are we expecting yet another centralised P2P like localbitcoins? Or are we talking about a Bisq-esque client where you keep private keys and escrows are smart contracts instead of central entity?