No kidding. "Oh, we'll just redesign the fuselage, engine, and avionics..." Geez, why don't you just design a whole new plane? Oh wait...
I had a chance once to talk with engineers - who wanted to sell the program, mind you - about a modification to the F-15 wing. It involved placing a small piece of equipment in the wing.
After going around it for a bit, they agreed it wasn’t possible. The ‘minor mod’ would force a redesign of the entire wing. The company trying to sell the product took the F-15 off the list of potential candidates.
I won’t pretend the system is perfect, but I wish folks would give the military officers working these projects SOME credit for intelligence and patriotism!