I had a plumber fired from a job after several problems (including not p-testing prior to completion of finished wall, forgetting to solvent weld FOUR CPVC joints inside wall, leaking drain line, HOT WATER supply to toilet...

).
After correcting all of those (at significant expense), I just discovered newest problem that he used nipples 1/2" too short for the flush mount Kohler body sprays. Although the instructions were quite clear, he failed to account for the thickness of the finished with with tile. The wall is now complete and body sprays won't attach due to the too-short nipples.
I need to remove the nipples from the copper els and replace with longer nipples. However, I'm working through a 4" square hole in the tile between studs and can't get my 10" pipe wrench to turn. Does anyone have advice for removing and replacing these from the end of the pipe?
Hopefully someone can help here or I'll be breaking out tile and backer board.
Cheers.