The issue with F-22 isn't the jigs or tooling, it's the avionics and mission systems. They are all based on obsolete 1980s technologies and architectures which are difficult to acquire and support. The F-15 architecture has moved with the times for export customers so is, essentially, "off the peg". You could consider retrofitting F-35 avionics to the F-22 airframe but, to be honest, it's probably cheaper to go straight to the Gen 6 F-X concept and buy updated F-15s to increase combat mass to fill the gap in the interim….which, I guess, is the USAF's opinion too….