Fair point. I suppose the reality is that it's a choice between biting the bullet and having purposeful cancellations (by that I mean ones during which people achieve training) in the short term with, hopefully, improvements coming sooner, or continued substitutions/overcrowding and real improvements taking longer.
The training won't happen by magic, something has to give. As Jingsmonty has said, it's a complex picture and things look pretty stretched right now - so, if/when the training can be fitted in is anyone's guess. Ironically, the lack of training will lead to more cancellations anyway. I just think it would be better to get on with it, even if some services have to be sacrificed in the short term.