You aren't entirely off target. For instance I do think it is dumb to have 21" wheels because that dimishes the performance and drivability of the car. Since this is a performance car, that kind of move is stupid.
The exhaust modifications on the other hand are okay as long as they don't bastardize the look of the car. These mods don't diminish performance but may enhance it.
Suspension mods are another gray area. Some enhance performance, some dimish performance.
2014 ///M5 Individual Frozen Grey, Silverstone Full Merino, Piano Black, Exec Pkg, Drivers assistance plus, LED Pkg, Bang and Olufsen, 20" 343M Forged Alloy Wheels
Countermeasures: Bel StiR+, Laser Interceptor Quad HP, Zaon MRX
Upgrades: Eisenmann Sport with M Performance Carbon tips, Dinan anti-roll bars