I'm trying to make bitmessage easier for developers and integrators. That includes a binary message format with easily extensible types. Check out:  https://github.com/Bitmessage/PyBitmessage/blob/v0.6/src/helper_msgcoding.py and https://github.com/Bitmessage/PyBitmessage/tree/v0.6/src/messagetypes . It's still an inactive proof of concept, but shouldn't take much longer to be available, probably in 0.6.2 release by the end of the year.