Motorsport is sort of similar where manufacturers build cars and there are independent regulations about the cars that define a class. There are spec racing series confined to single cars with very limited additions (safety) that are more oriented towards the driver in terms of competition (spec miata and spec bmw come to mind), but any international world champion type of sport is probably going to require enough monetary backing that manufacturer and aftermarket sponsorship is required to even afford to compete in the first place.

I don't think you understand how pro cycling works. Unlike other pro sports, cycling teams can't really sell tickets to spectators. Most of the revenue comes from sponsors for marketing purposes. So any change that makes it less effective as an advertising channel is a total non-starter.