I think this is a very interesting question.
The OP has given her view up thread-it's a shame to have to play the A* game, education ought to be about wider cultural things. I can absolutely see that, when they are younger, but for me, it ends at GCSE.
I guess from my perspective, I see it as more important that they can, at age 21, leave Uni and then use their creativity to think, what shall I do with my life, where shall I go? And sadly, too often what we see is graduates who can't make any such choices, because they have done uncompetitive subjects for A level and degree, and they are stuck.
I see a bigger picture perhaps, as I work in a university myself and have seen generations of students come and go, plus my own children and their friends are now early 20s.
My advice would be unwelcome, I think, to the kid in question. I think he has two options:
He takes essentially two A levels- English and history- plus a third placefiller. Of the three subjects he has in mind, any would do really, as long as he is confident of getting straight As in all three. So , make a pragmatic choice of the best taught and easiest subject, and for goodness sake don't do them all.
Or he can upgrade and do English and History, plus a modern language, if he wants a humanities degree, or plus maths, if he wants social sciences, or plus both, if he doesn't know what he wants. That would take him much further, and would be my advice, but it will also be more work and more risk.
In the end, it's all about delayed gratification. I enjoyed my music A levels- but I did three other competitive subjects as well. Music was just for fun. And it was the other three that got me my Uni place; and it was qualifying after Uni as an accountant that got me my job, combined with the languages. Music has stayed a much loved hobby.