If you are willing to overlook that deficiency in a trainer, fine, bring in the training FO TRE!
The airline that I currently work for has had two FO TRE's and they are both good at the job and accepted by all for all types of training and testing.
In today's climate with multiple redundancies common in a career people can wind up being First Officers for a long long time and even for life if they are unlucky. As long as the industry insists on seniority as the prime driver for command then that will be the case.
As one of the unlucky ones, frankly I get very fed up when some pompous arse tells me that there must be something wrong with me if I am still an FO and that despite nearly 10000 hours, more than half of it on my current type, I am unfit to pass on my considerable experience because I do not wear 4 stripes. The fact that I have training and testing experience in a previous life is dismissed as irrelevant just because I didn't join an airline on the right day.
Attitudes like that are the main reason that my imminent redundancy is causing me to ditch this whole rotten business and do something where ability and experience are actually recognised.
Given that Aviation in the UK at least will now only employ people straight from school, one has to wonder where the experience to train is going to come from, especially when existing talent is wasted in the way that it is.
I really am not going to miss it....