It is apparently true that one or two of the 'mentored' quasi-sponsorship schemes these days are tending to specify the subjects they'd like you to have at A-level, though I don't currently have references to say who wants what. I shall get them, however. If one of these schemes is your aim, you have to jump through whatever hoops they put in front of you.
That said, there are many more ways to get into airlines. None, so far as I know, specify any academic qualifications for direct-entry candidates. Until they do, continue to choose your subjects on the basis of what you enjoy and what you think may be of most use to you.
As for the 'equivalency' of the ATPLs to a degree, dream on! The ATPLs are an exercise in memorising simplified facts for a standard exam. While there is a great quantity of learning involved, the quality of the knowledge gained and demonstrated is pretty poor, and involves absolutely no free thought, interpretation, research or original work.
Scroggs