This would solve, or make it easier to solve:
- T383015: Allow undoing "marked translation unit as no longer outdated with no changes" edits cleanly
- T308425: Remove red links in translation units from Special:WantedPages
- T249361: Is there a better way for Translate to disable PST on messages?
And probably a bunch of other things, although those stood out from my review of the backlog. On the other hand dealing with all of the translation units in the database having a content model of "wikitext" would be a pain.