But at that stage what you want is effectively a messaging client with heavy to-do functionality, rather than some transformative. Bolting the to-do functionality on is probably a lower-hanging fruit than a new protocol.
Ideally you'd need a protocol system that allows for multiple data formats to be specified through a plugin mechanism to cope with things like social networks and SMS on top of email, but then you're squarely in the territory of being at the whims and mercy of constantly ensuring the plugin works with the backend data APIs for the services (for social networks), and sticking to the letter of the RFC law for email.
It's a great idea, but as they say, going to need a bigger boat.
Ideally you'd need a protocol system that allows for multiple data formats to be specified through a plugin mechanism to cope with things like social networks and SMS on top of email, but then you're squarely in the territory of being at the whims and mercy of constantly ensuring the plugin works with the backend data APIs for the services (for social networks), and sticking to the letter of the RFC law for email.
It's a great idea, but as they say, going to need a bigger boat.