Sunday at the bitcoin conference I led a little brainstorming session on extending the set of 'standard' transaction types, and I've been picking people's brains via email and IRC chat (and pull request comments) to work through the details.
My motivation for wanting to do this NOW is because it will allow features like:
+ Multi-device confirmation of spends, so if your computer is infected by a trojan it cannot spend all of your coins.
+ Master-key emergency backup, so if you lose your wallet (and all of its backups) you can get the master key from your safe deposit box and recover all of your coins
It will also enable third-party escrow and some other nifty features that aren't as important to me. The first step in doing all of these things is to work out the lowest-level transaction format and to allow those transactions to be relayed and included in blocks. That is ALL I am proposing right now (actually implementing something like multi-device spend confirmation will require a little protocol for the devices to communicate, a new kind of bitcoin address that people will send into, etc etc etc).
Working out a common way of doing (for example) 1-of-2-keys-required transactions will make it much easier for sites like blockexplorer to display them intelligently, and will generally make life happier for anybody writing tools that look at the blockchain.
I'd rather not have this turn into a "lets get rid of the IsStandard() check" or "lets re-enable a bunch of currently disabled opcodes", so if you want to talk about that start a new thread.
Current draft proposal is here:
https://gist.github.com/39158239e36f6af69d6f