This seems very complicated. The official line on threads for Tk has always been to make all Tk calls from one thread, which is at least predictable and comprehensible. Is there any reason for Tkinter to suggest anything different?

This ignores the compilation issue of course. FYI, the Tcl core group will probably eliminate the possibility of doing non-threaded builds in the future, though with backwards compatibility issues, that's neither here nor there.