He is suggesting that a commitment to continued work-based learning is what's needed to move from passive to active registration. This should not be difficult to achieve for working teachers because from this term, the new performance management framework requires schools to identify and meet teachers' development needs.
Bartley recognises the problems of bringing mature returners up to speed and keeping supply teachers in the training loop and that would need addressing. But on the wider point, the vast majority of teachers ooze professionalism. Anything that would help the public understand that and thus raise the professional standing of teachers deserves reasoned consideration.