Grample,
Welcome. I'm a convert from a Silverwing, although not nearly the years of experience as you on one, but a steady mover from scooters from 50cc>150cc>250cc>500cc to my current C650GT. I agree with many of your observations, the Silverwing was a great ride, reliable, semi-easy to work on besides all the tupperware removal, but it was older technology that needed a facelift and updates. For me the wheel size was an issue at highway speeds, especially on rough roads and the BMW has felt stable at any speed I've reached.
The Silverwing does have some excellent online support, information and parts availability as well as lower cost of ownership. The online presence and information is getting better for the BMW as the numbers of owners are growing.
I'm in the same boat with the 29" inseam but I ended up opting for the regular seat with heated option. I was a bit concerned at first, but as I have gained experience it has not really been an issue with one foot down or occasionally both feet on tip toes. I've found that sometimes it just easier to get off and push it around to park or move rather than attempt from the seat. That was a plus for the Silverwing. My only concern would be riding 2-up (wife has no interest anyways) as not sure how easy it would be to do the one foot down trick with 2 riders.
Overall, I was a bit unsure at first when I made the switch, but now I don't think I could ever go back. I only hope we see more aftermarket accessories and parts available in the future. (A nice set of modern hard cases would be my next upgrade...
Stay safe and enjoy the new ride,