I would be interested.
I have done 10 tours in the Alps in the last 13 years. I have gone with an American based tour company except for the last trip in 2011, when I travels without any professional help.
If I continue touring in the Alps in future years, now that I have retired, I will need to cut costs quite a bit. Your type of service would be of interest. At home in the USA I ride a Honda Transalp ... It is just my taste but I have never been any more satisfied with my rented BMW's then my aging Honda. I am probably not in the majority with that opinion. So your prices will need to a good bit lower than new BMW rates. I hope its possible!
What is very important is the dependability of the rented bikes. Honda are tuff and dependable when well maintained. I would rent one if it was.