Aero is quite regulated. So you can't play with wheel size, or various non-traditional bike designs. But other things seem like fair game, tweaks to geometry,

Aero is quite regulated. So you can't play with wheel size, or various non-traditional bike designs. But other things seem like fair game, tweaks to geometry, different bearing technologies, new bearing races, electric shifting, disc brakes, etc. The spirit of racing is that the race should be won largely by the best bicyclist, not the best bicycle. I'd expect a more efficient transmission would certainly be considered.