I’m uncomfortable with some of level of permissibility that this diagnostic is starting with, but frankly, that could very well just be my discomfort with format strings. I’d vastly prefer we be ‘as restrictive as possible’ at first, and visit loosening up restrictions on a 1x1 basis, but it seems that the submitter has uses for all the loosenings already, so I won’t stand in the way.
I think the RFC is acceptable as-it-sits now.