I doudt very much its the MPLs they will want rid of.
I suspect it will be the FO's at the top of the FO's pay scale.
I had heard that due lack of movement the whole flight crew pay budget was way way out due the the profile of experenced FO's they have with nearly no movement by the LHS either.
Might also find that they would have to pay off the rest of the training loan as well for the cadet intake if they made them redundant before the loan was repayed in full.