The MB warranty process states that all the paint must be removed and the vehicle painted from substrate i.e. bare metal.
This is what I would be asking for here with this S5? I would also NOT be settling with just certain panels, I would want the whole car painted.
You might also have colour mismatch concerns, with just odd panels being painted?
Also what if the un-treated panels "flare-up" in 2 years i.e out of warranty....