Hi
I know you literally said you don't wanna do it - but I am gonna have to urge you to consider S2. M3 & FP4 are fairly advanced units which would be mostly useful to someone interested in degrees in physics (M3), engineering (both) or maths (FP4). As a chemistry student, I think 3 FP units will set you up nicely for the pure maths involved (a lot of differential equations in chem) and mechanics is of limited use in chemistry. Statistics is useful throughout the sciences and general life and also I kinda feel S2 would be more interesting and useful than S1 by a fair ol' bit. There is also the consideration that S2 is a MUCH easier unit than the other 2. The only people sitting FP4 and M3 will be extreme A2 further maths guys like yourself, in S2 there will be a large cohort of people sitting S2 as their second year applied option (single maths people)- this is gonna translate to ez(ier) ums and help you get that 1 hunna.
At the end of the day, it's your choice - I agree that S2 might be a bit more boring than the other 2, but it's gonna be the most useful IMO and definitely the easiest. Why not go for the * eh?