As for the RN Operating a New MPA platform of any sort...
I don't believe it would be in the RN's interest to own and operate such a beast outright. the Manning would be a nightmare with respect to training sea time. It would end up that some of the Ground crew would never go to sea and that has never been an option that the RN AFAIKR.
The best option would be that the RN own the Budget and control of Asset comes under FONA down to squadron Commander. The WSO's are provided by The RN and Groundcrew and some Pilots provided by the RAF.
Just my opinion...