I would argue differently. Take a look at Rohloff hubs. Take a look at belt drives. Take a look at disc brakes. You've already dismissed everything to do wi

I would argue differently. Take a look at Rohloff hubs. Take a look at belt drives. Take a look at disc brakes. You've already dismissed everything to do with materials, oh well. Sounds like you just mean: bicycles are two triangles and two hoops... and you would be right. Strangely that's because the UCI restricted the development of bikes to ensure a level playing field, recumbents were banned in races, as were Moultons with their small wheels and pylon frames, as were the monocoque carbon frames, as were the bikes with farings. Ultimately, being restricted to two triangles and two hoops means that the manufacturers can only really innovate with everything else.