I'm already working on an early implementation in python with Qt and xmpp. A public derivation of the masterkey for generating addresses is much better than P2SH enforced. The server only need to store the public master key for each account and generate incrementally new Bitcoin addresses at each request. It work together with bitcoind and can easily be implemented as a plugin for electrum or any Bitcoin back-end... I see it as a great merchant tool for payment processing as a main target but even an auction market scheme can "easily" be implemented with this protocol and client software...
I would propose to call these servers not banks, but something else, as this has very negative connotations these days.
I fully agree with that.