About your rotors. Go with a stock type replacement. Not drilled or slotted. You can go to a better material. I think the BAT rotors should be fine.
Also, if your mechanic says your rotors are thin, then replace them. What he is reffering to is the amount of metal on the brakes. When you AutoX you'll be using your brakes HARD. When you do that they go through rapid temperature fluctuations. Thick rotors won't warp on you whereas thin ones may deform and in the worst case they can shatter(unlikely but I have seen it once)
Brakes are all about converting motion to thermal energy and then dissipating the heat. Thicker rotors store the heat better than thinner ones.
Hope this helps.
