Case in point:
We are in a bit of a bind because zebra and uncontrolled were both skunked or redefined so long ago. If the replacement of crossing=zebra with crossing=uncontrolled is unattractive to the community, then I would suggest omitting crossing=* altogether. This doesn’t require a formal deprecation of crossing=*, since a crossing node or way has never strictly required a crossing=* tag.
In my own city, where we had to map hundreds of kilometers of crosswalks to connect our imported sidewalks, we typically omitted crossing=* in a first pass. We didn’t want to take a side in the intractable debates about this key. Now that the deconflicted subkeys are reasonably well established, we’re able to sidestep the drama. People do add crossing=uncontrolled or crossing=marked out of habit or through editor presets, but it’s merely tagging flotsam; the precise value no longer matters.
I appreciate your courage in bringing any crossing-related proposal to a vote. The proposal ended up being fairly complex due to all the intersecting interests, no pun intended. If it doesn’t succeed, maybe you could try scoping down the effort by focusing on crossing_ref=* and crossing:*=* as a replacement without introducing any crossing=* tag as a replacement. Some will probably complain about redundancy or verbosity, but as long as the proposal is explicit about avoiding ambiguity while enabling the future regionalization of crossing=* that these mappers always wanted, then their concerns effectively become cosmetic and temporary.