I booked the car late last week so I don't have as much info yet. The sales guy told me that he could get the rims changed (at a cost of course, and I will need to figure out a way to get rid of the 17" 414s and tyres). So i'm going ahead with the luxury line, and getting 18" 397s on it.
I heard a lot about the run-flat issues, etc and asked about switching to regular tubeless. But from what I've read here and been told by the BMW guys, the new run-flats are a lot better comfort-wise and reliability over the previous gen. So decided to stick with the 18" run flats that would come with the new rims. Pricey, but saves some hassle that way.
I'll know what the deal is sometime this week once they get back to me with the details. I'll let you know.