Where? Well the Government and the MoD won't put them north of the border. The risk of spending millions on the infrastructure and support with the re-emerging threat of an independence vote would make that a non-starter, unless they want to use it as a lever. But that would be a massive political gamble.
Waddo springs to mind. Fairly central for the North and the SWApps. And it has all the secure connections.
Who? Well, the FAA would just love to take on maritime patrol. But they simply can't get there from here. They simply cannot generate that many trained personnel and everything needed to support them in the timeframe. The Navy has new ships to man. A whole new, big role is never going to happen.
How? Guernsey Girl, just saw your post. WSOs are in short supply. But, consider this; where will the money come from to fund P8? Something else will have to go in SDSR. Maybe something with navs based north of the border. Hopefully, this could be in time to harvest the seed corn in the west for the rest of the crew. How else will this happen?