I have a great disliking for chains. Having ridden shaft drive BMW's for 20 years I now have a belt driven model - brilliant.
Years ago I had an idea that transmission could be by hydraulic pipe. I think this has now been achieved as a front wheel off roader. By Honda perhaps. Why not persue this for the rear wheel [or should bikes become front wheel drive anyway?]
The looks could be made quite clean as would the bike become. The supercharged single appeals as does a reving multi. What about a disconnectable flywheel mass like a gear. This could then idle when not used or be brought in when need. Say having a multi which could also run on one cylinder.
You could have characterisics of both types of engine within one machine. On the issue of brakes. Why not have brakes which operate on the wheel rim a la push bike. The larger diameter could result in smaller disks which might be possible with modern materials.
Again the lines could become very clean. Again on wheels. Why not have a bike which could accept different wheel sizes for different uses. Thick treads for off road on a smaller wheels, and larger wheels for conventional road use.
Obviously I am not technical in the motoring sense but I do like thinking outside the box and provoking thought. Robin Leicester.