i dont think there's anything wrong with doing law at a-level, you should probably do another essay-based subject like english or history as well. i dont think universities particularly look down on people who do law, really, you can do any subjects and still get offers from good unis for a law degree so it doesnt really matter
i reckon a lot of people do law at a-levels because they feel it'll give them some sort of advantage at university but it actually doesnt! so i'd say if that's the reason you;re choosing it, you might as well pick a subject you like or are good at. but as i said earlier, if that's what you want to do, then there's nothing wrong with doing law at a-level