I think the big caveat mentioned in the editions section (https://without.boats/blog/changing-the-rules-of-rust/#editi...) still applies to your suggestion. The author concludes in that section "I don’t know if this is even possible to implement, probably it would have pretty bad effect on compile times at".

Your refinement seems like a nice addition to the author's suggestion, if it is possible and doesn't effect compile times too much. Hopefully somebody smarter than me takes a run at the problem.