It is a bit odd for a car though, you have to admit. Imagine buying an ICE car with a fuel tank that had an artificial limiter. Add 4 gallons to the tank for $x (120 miles). Would people accept that?
If the actual functionality is dependent upon Tesla’s systems, sure. Otherwise you’re just enabling a jailbreak market. There’s even precedent for this with Malone tuning.
I cannot find it, but a few years back I saw a car hack whereby you could buy a basic model car and enable some premium trim features (I think it was underbody LEDs) via CAN bus hacking - the hardware was present in the basic model car but disabled.
So yes, people do accept this even if they don't realise they're accepting it.
People will accept that. Pair it with a trendy automotive themed name that ends with the suffix 'ly' and pass it off as "a different type of car company".
Besides, Tesla will know the moment you connect to the ethernet port.