So, with the new custom part transpositions, it’s now almost possible to do something I’ve wanted for a long time… being able to produce a “modern” Horn in F part in parallel with <= 19th century horn parts written for multiple natural horns.
The only remaining stumbling block is that every time the “real” part switches to a different natural horn the modern part gets a totally redundant “hn in F” instrument change - and instrument changes are one of the things you can’t hide or otherwise suppress.