sorry for replying once more to this interesting ride.
Just Paul Brodies cruiser came to my mind last night and I have to share this here too.
His result as shown at the North American Handmade Bicycle Show (2021 if I'm not mistaken): https://www.thespoken.cc/paul-brodies-shaft-drive-cruiser-3
The shaft drive system can be still ordered from a company called Sussex in Asia, at least the website is still up an running https://chainlessbike.cn/index_en.html