Renault Alliance, Encore, and GTA, 1983-1987. Three different ECU types, all Renix. I'm sure that someone could figure out how to rechip and tune anything, but at what cost? They would remain a low volume project for anyone, so high cost.
What you are suggesting really makes about as much sense as building a model ship in a bottle. Sure a few people might be able to do it that way, but most people may just want to build a model ship.
The open option would equalize out the cost for everyone and allow the rare oddball car to still see the front of the pack for a while.
I am not sure that we have not refocused the purpose of our interest from racing to technology. Sticking with the stock system, which cannot be verified at the track or Joe's or some other system, that cannot be checked at the track will not ever cure the feeling that someone is taking an advantage. The ability to police the technology has already passed us by, from the factory or Joe's. Let's police what we can measure, the mechanical parts, open the rest up and race.
Carl