19 inchers on the GS was I am sure purely for marketing reasons.
I recall many a road test on the current BMW M3 at the same time reporting that 18" wheels gave a much better ride and handling compared to the optional 19" wheels... that also suffered from crack rims like the GS.
Heck the Trofeo 4200 ran 18" wheels and that was for track only!
I found some satin black concave wheels to emphasis rear width that ended up quite flush with guards I like them
But everyone has their own opinion on looks And purists hate u touching anything so expecting to get shot down but I’ll post up a pic so u can have a look anyway