ATG, so your idea is to put RN surface and subsurface operators in the air because it would be nice for them and retention draw?
From what I remember all the RN exchange guys I worked with on the MPA fleet in the past were all FAA?
The idea of wasting the valuable experience on single tourist is ridiculous and demonstrates a very poor understanding of what is required to generate and maintain an effective MPA force. RAF NCA WSOps spend most of their careers flying and build up a wealth of knowledge and experience, this is enhanced by cross pollination from other fleets. They are selected for the job at OASC on their potential abilities and aptitude to operate in the air. If you are advocating replacing these people with others from trades with less stringent selection processes you will not get the same quality output in the air.
The RAF didn't drop MPA in the SDSR, the MRA 4 position was untenable for a number of reasons and was a government decision (rightly or wrongly). The RAF provided an extremely effective force and it and would want to regenerate it again if it can be funded. In addition to ASW and other Maritime roles UK MPA were capable of many other roles, any new platform would do the same so little point providing someone who is just and acoustics operator.
There is no reason to reinvent the wheel on this, the RAF training pipeline can provide greater output if/when required, RN FAA operators will come on exchange. If aircraft are purchase they won't all arrive at once, skills and experience will build, provided people remain on the force
BTW which part of this All Arms ASW involves Land?