Winter wheels + tires for E70

[JensM]

Hi Forum,
I have googled a lot but have not really been able to find an answer, and I hope some of the Forum members can advise.
I got a 2012 30D MSport with 223 staggered wheels, and need a set of winter wheels & tires.
Current set up is front: 9x19 ET37 and 255/50x19. Back is 10x19 ET20 and 285/45x19
With the MSport wheel arches, the current 285 does even look a bit lost.
The winter wheels and tires I currently look at is 8,5x19 ET37 and 255/50x19.
In front it may look all right as same ET as current but 0,5" smaller. I am more concerned about the rear: 1,5" smaller rim and 30mm smaller tire - I am afraid this would not look good.
My question is therefore:
A) Either find a wheel with different ET - lower number I assume?
B) Use a spacer at the rear
C) Eventually go up in tire width at the rear, but not sure if this is recommendable on a 8,5" rim. On the other hand, a wider tire may not be that good in winter conditions (in Switzerland)

I hope some of the members have some knowledge or some experience to share

Cheers
JensM