Lowkoon,
Even (properly accredited) simulator providers have to comply with quite rigid regulations and whether training is in house or outsourced, at the end of the training a TRE is signing that pilot off as competent to operate the aircraft.
He is the only person that determines pass/fail or remedial training, if required. That is the final check and balance.
If he can be ‘bought off’ or influenced by his employer (the training provider) then the system is really broken.
I cannot disagree with any of your other comments.