DR,
While we could no doubt discuss at length exactly what you mean by 'MPA', I believe that your statement..
'...One can pretty much assume that within five years, MPA will have returned under a different guise....
is very optimistic. I can't see any politician admitting/accepting that the UK needs some form of MPA for at least 5 years. Add another 5 odd years before anything enters Sqn service, allowing for the procurement, production, delivery, training wheels to turn (even if we buy 'off the shelf') and crew experience levels will be a major issue.
10 years from now most ex-MPA crewmembers will have left the RAF by one means or another.... Many of them will be leaving in the next 4 years, and many others won't be retained beyond their next option point.