It has always impressed me how many wall join videos I can watch and still find that there is yet another permutation that has not been formally addressed yet. In my opinion, it is one of the thorniest programming problems Revit faces and it would be wonderful to finally face it and resolve it much more thoroughly. I wonder if there might be a way to introduce a graphic lexicon for "special" wall joins prior to a cadd user making the join they know will be complex. I'm thinking here of something a little like the Fry Reglet "shapefinder" tool they have to help customers find the right piece of metal.
https://fryreglet.com/shape-finder/
Instead of showing a bunch of shapes, there could be a series of join configurations starting perhaps with 2 wall, 3 wall, 4 wall and perhaps 5 wall joins. I know this would be an involved interface but again, it would only be used for "special" wall joins. Just a thought for a problem that has really persisted for more than a decade. It would be great to finally solve this.