Smokie
Whilst I'm no fan of the MPL scheme, I don't believe it has become a joke because some guys have been able to transfer types/companies.
It's purpose isn't to hold you hostage to one type/AOC; it is merely a change in training philosophy, one that encompasses more multi-crew operations rather than light aircraft flying, as it's deemed more relevant.
Again, I'm not it's biggest fan, but I am under no illusion - it is the future, and I actually agree with it, in concept.
I fly a B777 after flying nothing larger than small twins and turboprops. I can assure you that such GA flying, whilst fun and a good experience, is sod all use when it comes to handling a 350 ton jet, ETOPS, HF, polar ops, etc.