Talk about switching back to F35B is foolish now or going to a fantasy Sea Typhoon. The program needs de-risking and the cost of the F35C needs to be pushed as far as possible to the right. Nominal OSD for Tornado GR4 is 2025, thats when really need F35C as a replacement for that type in the penetration strike role. With current build schedule we probably won't have a carrier fitted out with EMALS and AAG until 2019, that means we couldn't even conduct deck landing trials until 2020! Those landing trials can be conducted with American and French help using the Super Hornet or Rafale. Post 2020 they are talking about operating about six aircraft on PoW during that initial slow work up period. Rather then take the riskier, costlier early F35C this can be done with a lease of Super Hornet or Rafale. It will take about ten years to be in a position skill wise to operate a larger airgroup of 12 to 36 aircraft.
This gives a lower risk and cost schedule:
Operate leased Hornet or Rafale until 2030 with F35C test airframes making occasional visits.
Draw down of Tornado GR4 by 2025 with new F35C taking on role along side Tranche 3A Typhoon from mid decade.
Stand down of leased aircraft around 2030 with F35C purchased from later and cheaper production run of the type entering carrier service.
On a side note if the will is there QE can be dragged back into Rosyth in the 2020 to 2030 time period for a refit to CATOBAR configuration. That keeps skills in Rosyth that would wither otherwise and dovetails with the significant overhaul PoW will need after more then a decade of service.
De-risk the program, de-couple the aircraft choice from the carrier build program and push costs as far as possible to the right in respect of F35C. The USN plans to have the F35C in service for a long time procuring LATER will be cheaper then taking earlier examples!