I AX mine in BMW club, but don't think it'd be competitive in SCCA AS. You need way more negative camber than you can get out of the stock suspension. You can change stocks in AS, but not springs or ride height, so there's very little to gain on the suspension side. The tire sizes that you're proposing will be at the outer limit of what will fit the stock rims.
Regarding sway bars, you don't need more stiffness in the front. Go with the E93 rear bar to stiffen the back a bit and improve rotation on tight AX turnarounds. The brakes are fine and all you're allowed to do is swap pads. I'm going to Stoptech's street/performance pad next year to see if I can get a little quicker initial bite, but I'm not expecting to gain much time there. I'll also go stainless steel, but I think that's not allowed in AS.
Unfortunately, AS rules don't allow changing the final drive ratio. My 4.10 ratio really works well for AX.
Regarding exhaust, you're limited to cat-back mods and you must still comply with sound limits at the venues. Check your club rules. Opening the back of the exhaust isn't going to gain you much anyway.
Go to a high-flow air filter, which'll gain you around 6-hp.
As you say, get as much negative camber as you can in front, but keep the back at one-degree or less. Run the back pressures at around 28-psi cold to improve acceleration traction and improve rotation.
Still, if you value winning, then this is not a good plan for AS. The car's too heavy vs. the competition in this particular class. Go futher, with coil-overs, final drive, power adders, etc. and join me and many others in BMW or other marque club AX events, where the rules are much friendlier.