Trying this out with vanilla and it seems to work well with the latest patch, although I have a question as to why in the 1337 start, England is not the preferred title of King Edward III who chooses to take Wales as his primary one... Any ideas for that, mate? I'm not sure if it's the same with CK2+ although I do not think so. That might be a vanilla thing.
Figured it out -- k_wales still has extant entries. k_wales.txt with everything #'d out fixes the issue immediately. This is only relevant for people who want to play it with vanilla. CK2+ already has this in there.
Thanks for letting us know .