Listen to the guys from Alaska, they live with it.
I was in the Yukon and NWT, and only went to Alaska for vacations (the full length of the Alaska Highway, with detours to Skagway, Chicken, Dawson City, etc).
I would put a priority on being able to see, so if the windows were fogged I would wait. None of this stuff can be taken to an extreme. The thinking on the stiff seals, gear lube, etc, is that engine heat will have little effect on remote components. It all comes down to minimizing the warm up time, and believing that the faster it warms up, the better. It is still a judgement call, and I had to let my vehicles idle more than a few times.
I started vehicles outside at -40 lots of times, and as stated above, they start. Agree, they really don't like it very much, and anything is off (oil viscosity, battery state, etc) they may not start.
I like the stick-on heaters on the oil pans. Anything like that helps. We used them on industrial engines, usually gensets in places where we had to go through black starts occasionally. Portable gensets to get the main engines heated, and then working up from the smaller engines to the larger ones.
The idling problem has to do with the crankcase ventilation valve freezing, but it doesn't happen after one or two occurences. It is statistically more likely, that is all. I don't think there is anything unique about a BMW in the cold vs another vehicle. It is just that the parts (and repairs) are more expensive, and BMW really doesn't have much experience in very cold weather. They are naturally cautious.