I honestly don't think FADEC is an issue at all for training. There are far more differences between e.g. a DA40 and a typical school plane, not least that a DA40 will have a lot more stuff in the panel and, being a new aircraft, the stuff is likely to work!

I did my PPL in C150s, PA38s, C152s and while all of these had a mixture lever, nobody ever told me what to do with it, other than shutting the engine off with it.

And if someone has done their PPL in a DA40, they will never want to get inside, let alone fly, anything else that is normally on offer!

Last time I spoke to Diamond the diesel DA40 was listed at about 160k + VAT so I don't think everybody will be worrying about this anyway :O

...well, not until Robin or Diamond stick a cheap diesel into their 2-seat trainers that is! :E

Well, I don't think learning in any new aircraft is realistic - as it is unlikely to get most club aircraft to have everything working as mentioned.

Teaching non-FADEC engine operations will soon become what the other old practices will - such as prop swinging or whatever it's called.