This is something I've wondered about. For cars there is a bunch of regulatory stuff that might preven you from doing this, but I believe the regulatory burden on tractors is much less. Why has no one just built a full on control system swap for tractors? Yeah, the OEM control board won't recognize your replacement part. Or it won't tell you whats actually wrong. Etc. Etc. But if you just replace it with an entirely OSS control system, that problem goes away.

I know that this probably not a trivial task, but, given the amount of money at stake, it feels worthwhile, but maybe I'm just underestimating the degree of integration of the current control system into the parts. If everything down the internal engine sensors is running priprietary, encrypted software and you basically have to tear it down and replace every single electronic component on the tractor, then yeah it probably won't ever make sense.