The problem with off road training is it is just that all it can ever do is give the new rider the very basics of riding a bike. Perhaps in the CBT there should be a compulsory amount of hours on road training. Having been an instructor though a few years ago you can only teach so much, hopefully enough to keep new rider out of trouble until they made their mistakes and have learnt by them. I agree with training for new riders, but it must be remembered good as most instructors are they don't possess a magic wand which can be waved to instantly provide the experience that builds up over many years, and dare I say it a few of those experiences are often very painful I know some of mine were. One piece of advice I was given when I started riding was treat all other road users as complete idiots and you wont often be disappointed.
I think a licence in stages as for motorcyclist depending on age would be a good thing.