Exactly for the reasons you list - it'll never happen just like the government implementing a reliable and affordable public transport system will never happen either. It's ll very nice in theory but in practice the cost of implementing a reliable and effective tracking system as you describe would cost billions and it just won't happen. Now if you are talking about specific roads being ' toll ' roads to reduce congestion as they have done in central London , that seems more viable and if it makes people stop and think before making unnecessary journeys thus reducing the jams and reducing polloution and carbon immissions then bring it on. We can't expect to carry on like we are without having to pay for it one way - either sooner or later we'll have to pay for the environmental damage we create.
Just for your info , road tax in the UK is amongst the chepaest in Europe. Sure your fuel prices are a bit higher but not so much any more if you look around the rest of Europe. I used to run a diesel engined VW van in Holland and it used to cost about GBP 200 per quarter so 800 quid a year plus the cost of the fuel to run it which wasn't exactly cheap either. It was a 1600cc engine so not a high powered engine by any means and the MPG was phenominal so in retrospect I'd certainly prefer to have been paying UK road tax then or even paying per mile of use then but I had the choice to drive it or not.
I agree with your principle that freedom of choice is important and civil liberties need to be protected but such a scheme as you describe is science fiction and is unlikely to happen in our lifetimes. The legal protests on the grounds of civil liberties alone would ensure it was delayed for decades.
Ride safe keep it rubber side down

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