but i dont see any need for manual focus rings on "regular mainstream" AF lenses any longer given today's technology
Automation can work great and deliver potentially superior results. But it can also kill the fun, the satisfaction, it detaches your involvement with your work. As I see it, dedicated cameras are mostly enthusiast products these days. And they should offer all the controls they can, so that somebody who is willing to do that can get as involved with his or her imaging as they care to be. Just because all settings could be accessed over a screen, and the images would likely be the same, the shooting experience would probably be less pleasant for a large number of people.
To get back on topic, it seems common knowledge that a smaller backfocus distance allows wide angle lenses to be smaller than their counterparts for higher distances.
Do we have some reference for the way image circle size affects lens size? I think it's right to assume costs increase with larger image circles, but would an 50mm RF-S be any different in size than a 50mm RF for FF? Would it be different at other focal lengths?