Thanks for the detailed explanation Eryk. While it is a little annoying that it comes 2 years after the initial proposed solution, I'll happily take that if the end result is a better fix :)

That being said, this fix seems quite a bit more involved to implement than the previous one. While I am now slightly more experienced in contributing to Python than previously, I'm not sure if I can commit to implementing the outlined changes without some help. Some things that would help out a lot:
- An extracted checklist from the rather longer comment?
- Writing up the requirements as tests cases so that I can do test-driven development (I'm not very familiar with the testing suite).

If somebody else would want to either do it themselves, or help out with certain parts, I'd be very open to that (I'm not trying to "own" this).