There is a plan (or at least the desire) to put Meteor on the F-35B, which would be helpful. Engines might know whether the B can carry four internal AMRAAMs or Meteors, with the outboard internal bays being shorter than those on the A/C.
However, another snag with the ideal stealth air combat engagement is if the RoEs call for identification and by what means. Euro and USAF philosophy is not always aligned on that issue.
C-S - I would not bet against that schedule.