Not exact matches
The idea of using 2of2 multisig is original but the end result is likely to be the worst of both worlds: you get the disadvantages of old school brokers / exchanges (full ID required, trust in centralised platform) and
regular client - side bitcoin (you're screwed if you lose your secret, you need to trust the
wallet software provider).
Bitcoin exchanges are not built to work directly with the Bitcoin protocol like
software wallets, so they can create problems for users who want to make bitcoin payments on a
regular basis.
The convenience of online and
software wallets makes them ideal for small,
regular transactions.