yeah agree with all of that. the only reason i thought about 3 bits was (1) we had room and (2) it is 50% more bandwidth for when someone inevitably makes an insane video codec with this 
To your header I would add some version information so like SOH VERSION # TYPE<mine> so we can migrate a protocol and replace text with binary but otherwise agree completely
despite my strong desire i’m not going to write an encoder/decoder this weekend but would happily review, use, comment, collaborate if you want to. Or if you aren’t going to I might do it later in the week.
what a nifty idea.
oh and I guess we should make sure the idea still works for @StochasticTelegraph
oh and if we do it the first module to write is a ‘text scope’ of course.