wouldn't recommend taking Advanced English unless you know you are going to get high marks on it; it's not a walk in the park. 2-Unit Mathematics looks like a good foundation for the type of university course you want to do (you'll find yourself applying exponential/logarithmic problems in the mathematical end of the business sector). All the others seem to suite your course also. So, apart from advanced English everything looks pretty in order.
But yes those subjects look fantastic. As someone above me said, unless you're good at maths you'll get smashed. I did 2U maths and epically bombed out. I wasn't terrible at maths, I got a band 5 in the school certificate and studied my butt off but 2U maths is a LOT of work. I did 10 times the amount of study for Maths than anything else. And I got half the marks. I got over 85 in all my subjects. And 73 in maths. I wish I'd dropped to general. If you think you're ok and you go alright through year 11 though you should be fine. I mean you can always drop to general.
To the person who said do standard english, definitely don't. You seem very well spoken and can obviously string a sentence together. That's all you need for advanced maths. Only like 2% of kids get a band 6 in standard english. It's basically a subject for those who don't really care about their HSC. Advanced english really isn't that tough at all. I think I did about 5 hours of study for it the entire pre-hsc period. I got 88. And I'm not a natural at english either. I had a fantastic teacher and again, it's not that tough a subject really.
Another issue is MAYBE you'll have a problem with both economics and business. I didn't do either but so many people in my year hated economics and slept through business. I mean you can always drop a unit but still... Remember economics is a hard subject. It scales well but it's hard.
Modern history was my absolute favourite subject. It was a joy to study (that sounds so nerdy). But i honestly loved it. It was my best subject with 94. I honestly think I could have gone better but I spent all my time studying for everything else because I thought it would be a breeze.
I wish I'd done legal. Everyone in my year loved it.
As for scaling... I was obsessed with it prior to the HSC. In reality I found it was totally irrelevant. But this site has a full list of the scaling of courses. It's old because the board of studies are now nazi's about giving out RAW marks to people they think will use it to figure out scalings
http://www.boredofstudies.org/scaledmean...
Check out the other resources on that site. Got me through the HSC seriously
But yeah that's my opinion. If that's the path you want to go down then choose all three, what's the point in doing something else