It would be better if the Chinese simply won't allow anyone to come in to work for crappy training centres. Some problems would be the solved automatically: Training centres would for the most part cease to exist because they can't find any foreign teachers or "teachers; much less problems with crappy recruiters and agents, and finally less cheat and deception.
It would come up to some kind of marker cleaning.

Another possible result due to a possible high turnover of mugs, could be that Training Centres end up having a fresh set of newbie naive mugs to rip off every year.

The other problem with a returnee going back to a Police Check is that they will have not been in their home territory for maybe a year or more and there the Police Check will state this because it would be part of the Police Check application to say whether the applicant has been overseas in the past few years..

Fact is that a teacher who has been in China for a year should actually get a Chinese Police check because that is where he/she might have or have not been offending (or not paid bribes).....

Meantime I am actually surprised that Training Centres haven't jumped on the "Volunteer Programme" bandwagon..