SFO
Why do you think the USA have gone for a twin pronged approach? The study the DOD commissioned on replacement of the P3 concluded that, whilst RPAS platforms could bring something to the party, you still needed a manned platform (just not so many).
So either Uncle Sam has got it wrong, or we know better.
If you're still at Preston/Warton then get a visit to the hangars/buildings on the south side and ask them whether they think it is possible. The study you talk about for P3 replacement happened a few years back and things are advancing fast since then. Have a chat with the UAS team and I'm sure you'll see a different perspective.
LJ