Think they'd (Marshall) be mad to consider taking on the running of an old MOD base like Wyton or worse still Mildenhall from say 2025 - think Alconbury is out because they are already have housing plans in the wrong places? The overheads of running airfields like that would make running CBG look like a kids tea party. Why own a huge piece of airport infrastructure in the middle of nowhere which nobody else needs but you - and it's not going to be a land-bank for housing of any grand scale if all goes belly-up if it is in middle of nowhere. With 2022 looming and the Herc C130 contract presumably (?) coming to an end, how many huge sheds will they need in the future, certainly not as much space as they have now? They do work on big Boeings in the civil sector, but they don't really make money out of that stuff - that's not core business.
Far better to keep all the design and back-office and small shed activities, workshops etc. still at Cambridge, on what, by default, will remain in part an industrial estate a new business park, next to the 12,000 houses, then for the actual aircraft MX activities, be at someone else's operational airport - they can pay the bills to run the airport side of the equation! If they want to retain the bulk of the CBG engineers, go and buy the Diamond hangar at Stansted - plenty of space on one side for expansion, or just past the Ryanair shed. If they are prepared to lose say half the engineers who won't relocate (not likely to need as many as they have now anyway?), then move MRO (hangar-based) ops to Brize Norton. If that doesn't stack up politically, then last choice is Cranfield. The only ready-to-move-into hangar is the Diamond Hangar at Stansted. Wyton's are too small with no ramp elbow-room - they'll have to build brand new facilities wherever they went.