So something that improves your health, reduces obesity, reduces disease burden on the NHS etc has to obstructed by licences and red tape? Where do you stop? What about licences for pedestrians (who may run their key along the side your car)? Children on those little push things? Old people on zimmers? I mean they have wheels and could bump into a car or cause a scratch?
Something the like of which every recent government has been desperate to promote.

Even if it was a great idea, I can't see it
ever gaining any political traction.
It will turn every cyclist against them (a growing sector since Wiggins fever got all the mamils out on the street), 1% - the aforementioned "they don't pay road tax" band will be all for it and the other 99% of the populace won't be bothered or maybe won't even read that far into the manifesto.