Lonewolf, I think you are right about only needing the C compared to the A, but I am not sure that your point about the B is as valid. Anytime the US are doing serious fighting requiring that sort of capability I think there would be a carrier around which would also generate more space for helos / Osprey.
The real problem there, of course, is the USMC reliance on the USN and their loss of control of fixed wing assets to some degree, which I suspect is their real issue.
I accept there may be niche cases where a VSTOL version would be useful, but given that it is far inferior in terms of payload, range, manoeuvre as well as being far more expensive we may be at the stage where even the US of A can't afford it.