1) Mine wanders left when I take my hands off the bars. I would not call it a "pull". So did my last 2 street glides, I think it's the way I sit (although I also had a tendency to keep more gear in the left than the right too... A little knee pressure to the tank or a shift of weight to the right straightens it out.
Then you don't have the pull to the left. If you did, it would be very noticeable. What happens is the bike starts to wander left then the speed of the deviation picks up, forcing to to correct immediately or you will dump it. That's good to hear.
2) I've never noticed a buzz. I ride with gloves 100% of the time.
Very good to hear.
3) I can't imagine how a tank bag would fit over the fuel filling area. I have the black handlebars. That area is very tight. I can imagine mounting some sort of pouch to the bar though.
I figured this but the utility of the 'regular' bars (and they're black) outweighs the small amount of times I would use a tank bag.
4) No, I have not. For an iPhone to work, you need to use the BMW splitter. I don't know how long of a Lightning cable you can run to the front of the bike, or conversely, run the USB/Audio cable and use the splitter closer to the destination. I would think doing either would make it ripe for picking up noise though, so you'd have to get a pretty good cable. Why do you need the iPhone on the bars, may I ask? GPS (assume you aren't getting the Nav VI)? You can control the iPhone music functions through the stereo.
I can reroute the wiring as necessary. Shielding is not a problem. Used to build experimental aircraft, including a fiber optic control system, so that's in my wheelhouse. I want the iPhone on the bars as I use apps like Waze to avoid the inevitable tickets without it. Found a sneaky LEO yesterday using Waze. The guy behind me wasn't so lucky. He had to be doing 90 when he passed me as I coasted to just over the speed limit.
5) Haven't tried yet, seems like there is more than adequate space to do something there. I think your questions have more to do with the type of bag/mounting system you get than the "B" specifically though? I'll be looking into that next year too. There is a backrest and rack that someone came up with, there is a thread on it around here. It's not what I'd call attractive, but it's an option. I've not specifically heard of BMW doing anything, there were rumors of a trunk, but that turned into the Grand America and is not a retrofit to the B from what we read.
I'm fine with the permanent mounting of the side bags. I never took the panniers off on any of the BMW's I've owned over the years, so they might as well have been bolted on. Only advantage was when I washed them.
I did speak with the BMW rep at the NY Motorcycle show. He showed me the bolts on the Grand America that have be to removed to slide the topcase off the rails that hold it in place. He said they were working on a removal kit (I guess it would have some sort of blanking plate) but had no idea about timing. For the K1600B, he said he had been told just that day that there would be some sort of rack for the K1600B but again, no real details or timing. And yes, there is no swapping at this point between the Grand America & K1600B. I would have gone for the Grand America but the grab rails are silver, which would look odd with the topcase removed, imo.
I have seen the one aftermarket rack for the K1600B. Nice attempt but it's pretty ugly. What BMW did for the Grand America is have two rails that extend back from the sides of the passenger seat like a fork. The topcase slides onto them and bolts in place.