I am not sure boundary=political is best, it is a dart on the board, and not on the bullseye.  It may be boundary=historic works, this is all very liquid.  I think this needs a wider discussion medium than the narrow bandwidth of a changeset comment.  I welcome a new topic in the USA section of our Discourse forum.

This all seems do-able, but it always benefits more from a wider, deeper audience.  So, while you might choose to "worry," tossing it to a wider discussion is prudent.  I wouldn't say I "took care of it," I "hit the dartboard but not the bullseye."

If you think border_type=planning_region can stick (and now that you mention it, I can see this sticking widely across many states), it's beginning to roll down the track of getting nailed together.  We lay down some track here and continue with wider discussion.