Unfortunately, such a thing will never exist, at least in a road legal sense. No government is going to approve it if it can be modified by the user. At best, you can have "look but don't touch" kind of open backed by some company if it has to be road legal. We aren't even fully over wifi router firmware yet.
Yet people work on their brakes in their driveway all the time. Hard to imagine a government allowing that.
Are we heading toward a future where it's illegal to drive your car on the road if you have modified its software?