Well, that's sort of the point: this is already possible, so in that sense nothing would change. Changing the mapping (essentially the amount of fuel injected based on a bunch of parameters) is regularly done by 'tuners' (between quotes because they don't really tune anything, they mostly burn more fuel for questionable gains).

But that's really not what I would care about. I'd like to read that code to figure out what the failure modes are and what might impact my safety in a negative way.