Based on the advice above I ended up with
Front: 235/40R18 | 8.5J ET35
Rear: 265/35R18 | 9.5J ET40
As explained I did not want to go all in, but just compliment the original design.
At this point I am 100% satisfied with the result. The wheel design turned out to be 95% OEM, while noticeably lighter. Also everything seems to be a perfect fit.
I absolutely love how all of the mods on this car are still undetectable unless you really know the E89-series well:
