S-D - The F-35B is all about coalition ops - US commanders are very clear about this. I can see that the USMC will be very interested in two carriers that can sustain 30+ F-35Bs but only carry a dozen or so (at least until 2023-24) because the UK has only 48 jets in total. That's because the LHA/LHDs, as big as they are, have much less capacity for jets because of all the other stuff on board.
Remember, too, that the US has a vast element of control over partner F-35s, at all times.