OK.
1) this idea is baked enough for cross-area review to make sense.
2) the protocol is not going to change significantly, one could
implement.
3) any future changes need thus to take into account impact on
existing implementations... BUT that doesn't mean that we can't
change things.
I'm very nervous about changes to the process of this form.
I'd support doing this sort of categorization as an advisory label.
For example if people wanted to get together and somehow track what
documents were fully baked as a service to the community and see how
useful it was, I'd support that.
I am strongly against making something like this a formal part of the
process without something informal like that first and without
significant experience with the informal something.