Blendmount has a mount now for BMW mirrors. Pricey but awesome. Got mine the other day, and my V1 just came back from Valentine last night (I'd sent it in for an update as it's over a decade old.) Can't say enough about how awesome the Blendmount is; I got out of the habit of using the V1 just because suction cup mounts SUCK ASS and it's distracting trying to stick your RD to the windshield while driving - your accessories shouldn't make you *less* safe.
I decided to go with the fuse tap rather than going into the roof, got the phone cord run down to behind the glovebox last night, wow, that was a PITA, took way longer than it should have. It's snowing now so installing the hardwire adapter and fuse tap will have to wait