Tks for the kind words ref ATC effort,....yup, the envelope does certainly on occasion become somewhat elastic.
Ref conversion courses, to current date, no, however, that does not translate to all is lost. If you have an App Radar Rating but have yet to validate it or it was on a previous occasion validated, but has since lapsed....well lets just say negotiating with a rating, current or not, is still a strong vantage point.
From a personal perspective, whether from an En-Route pool or App pool, ATC's that wish to be successful at OTBD need to have worked traffic loading between at least 35 to 45 p.h. There are sessions where this mark is substantially overshot, but from a trainability approach, ATC's with the aforementioned experience should adapt easier.
Our in-house sim is ops ready, but due various reasons has not been used. This is shortly to change such that benchmark App radar exercises (site specific or generic) will be promulgated and used to assess trainability of prospective controllers.