My understanding of the F-35 Sqn structure is that each sqn will consist of c55% light blue and 45% dark blue irrespective of the number plate. Personally I believe this to be flawed and foolish, but it will go some way to disguising the Navy's' inability to fully man their posts, in much the same way as they struggled with JFH.
As for basing, Marham is likely the only option given the eye watering amounts needing to be invested down there.