I did Maths, FM, French, Economics and Chemistry AS levels.
If you are good at Maths, doing further maths isn't too difficulty if you're willing to work and work fast! I managed to get AA in the two!
French AS is hard, but good fun (i found compared to chemistry, which i have now dropped because it's so boring, but you may be different!) and if you're good, it's a good subject - and applicable to ANY career, unlike history.
However, if you want to do law, do history/english lit (which ever you enjoy more), but certainly do Maths and Chemistry, or medicine is off limits.
I would say Maths, Chemistry, English/History, French and FM (if you think you can handle it).
I got 3 A*s, 6 A's at GCSE and i handled the 5 AS's - got aaaac (c in chem), so it isn't too hard, but you'll want to drop one at A2 i guess.