They already have an aluminum subframe.
Rims weight roughly 18-22 lbs if they are 17's. Buying aftermarket rims will just make things weight more unless you spend a stupid amount of money on rims that are like 12-15 lbs. Any tire in that size is going to weight roughly the same aswell.
There really isn much weight you can remove from the car other than taking all the interior out/spare tire etc etc.
I'm sure you could remove a couple items in the engine bay to reduce weight, but in the end we are talking like 20-30 lbs if that. Things like the engine pull brackets and the engine cover.
Factory exhaust is likely lighter than an aftermarket because they use bigger piping.
