Most people will tell you not to take physics so I won't bother touching on that.
As for studio arts, I did this in Year 10 but dropped it halfway through unit 3 because crap teacher + hated the class in general. I think I would've been more suited to art than studio art, but that's just me. In Studio you'll have to complete a folio as well as some theory (I like to think Studio is 80% prac and 20% theory, whereas art is 50/50). The theory is what I didn't like so much. You won't do much (if any) on art history, but rather you'll be looking at how art galleries work, the jobs involved, etc. You'll also look at how to keep your artwork in good condition (how to store, temperature, etc.) and you'll look at at least two artists which you will have to compare and contrast in the exam (in terms of style, historical context, etc.) If this sounds good to you I say go for it. If you work consistently on your folio and make good use of class time I think it would be manageable.
Can't comment much on politics but I agree it looks interesting. If you haven't already it might be useful to look at the study design or talk to the politics teacher at your school so you can get a better overview of it.
And lastly, what do you plan on doing at university? If you're thinking of doing science but have an interest in art then you might like to take art in Year 12 because you probably won't see much of that once you're in uni. Just a thought.