The problem with that is if you give a toss about net zero (putting aside the madness of it), then that doesn’t encourage more economical engines. I’d be half tempted to buy a 20 year old car with a 6 litre V12 if they came out with a system like that!
I’ve long thought that fuel duty is the best tax overall for the following reasons:
Drive more, use more fuel, pay more. Drive less, pay less
Buy a more economical, more fuel efficient car, use less fuel, pay less
Drive slower, pay less. Thrash the car, pay more etc
Easy to collect, impossible to avoid.
I appreciate people are moving to electric but take up is not where the government would like it, so they could further encourage people by punitive fuel duty rates.
I would not like such a scheme btw, I just suggest that if screwing UK tax payers is your objective, this might be a good way to do it. It also has the advantage that the government can lie about their intentions, passing it off as “sorry, but we’re forced to do this to save the planet - it’s nothing to do with us trying to shaft everyone”.