Resolution: proposal accepted.
No objections in above discussion, and positive opinions (đź‘Ť) from a few implementors on the proposal.
Proposal implementations in mf2py and phpmf2 parsers, and https://github.com/dshanske verification that phpmf2 implementation satisfies use-case for the issue is sufficient to demonstrate implementability and utility, all as noted/linked in issue thread.
Editing specification accordingly.