It is essential to have some sort of other education and preferably work experience you can fall back on. In this light, it is perfectly ok to pick your A-levels according to your best ability. If those subjects are what you can excel at academically, they will lead you to a matching degree with good grades, and motivated work. Which is a much better back up than a mediocre engineering or science degree that never got you a job because you chose something you are not good at, just for its "relevance". You might give it a thought to get into a field that could be used in aviation, because it might give you valuable contacts for pilot jobs, as well as keep you in the business should you encounter some kind of medical trouble or whatever, that could make you an ex-pilot. (Yeah I know, not the primary thought for a 16yo, but itīs a reality - **** happens everywhere). In this case, you would be better off switching to one of your airlinesī ground departments, than having to start over with something you havenīt looked at for 10-20 years, with an old degree.
Other than that, if you can do your PPL at 16 and talk about "getting your" ATPL just like that, you are probably comfortably sponsored by your parents. So all in all, with a privileged outlook to getting a degree and then obtaining an ATPL with no significant debt, you stand a good chance to ride off the rougher waves of the aviation business.
Just go on with what youīre doing, your folks seem to have money and you have decades of time to shape this out nicely, which puts you at the top of the wannabe food chain already.