Assuming this article is correct and Mildenhall is indeed closing, I don't see any other solution apart from relocating both forces Rivet Joints to either Fairford or Lakenheath. Lakenheath has the close proximity for airmen and support crew but will be full of fighter jets and does not have a runway of any more length than Waddington now. Fairford on the other hand does have runway suitability but infrastructure upgrades will be necessary for the additional 400 or so airmen and women.
Which location would you decide upon?