As others have said, road tax doesn't exist anymore it is VED. Car drivers would be cutting their noses to spite their faces if they insist bicycles pay VED. I mean how many billions of pounds would it cost to implement such a scheme? And for what? bicycles will be rated zero emissions and will have to pay NOTHING. Such a ludicrous scheme will be at the tax payers cost, and the Government has far better things to spend our money on. It'll also be nigh on impossible to manage, they can't even manage it properly with cars, let alone bicycles.
With regard to MOT, again what's the point? It will again cost a ridiculous amount of taxpayers money with no benefit to society at large. It's hardly going to save the NHS billions of pounds is it? In fact it will probably end up costing the NHS much more when people pack up cycling altogether and contribute to clogging up the wards with a variety ailments due to lack of exercise.
As for insurance, good idea in principle, but when does it stop? Should everybody have to buy 3rd party insurance anyway? After all pedestrians probably cause and are involved in far more incidents than cyclists, whether it be walking in front of a car or knocking over half a shelf of pickles at Tesco etc. So shouldn't we all be insured against every possible eventuality? Many adult cyclists will have some form of insurance anyway, whether it be through the likes of the CTC or their household insurance.