I think you'll find that Lusty was still on the Tyne (or at least in UK waters) when Hermes returned to Pompey in June 82. Lusty then relieved Invincible to return in September - the three were never simultaneously in Southlant, let alone the TEZ. During the air war (May-June), loss of one (particularly Hermes) would have meant Endex.
As far as alternates went, Rusty B had been so heavily stripped she was a non-starter and the oft-quoted US carriers were Essexes the last of which (Oriskany) had gone to reserve in 73.......