Lots of guys fabricate a caliper mount and use aftermarket or other brand calipers. As for swapping rotors, there are some Yamaha rotors that are close to a bolt-up, but you'll either need to fab an adapter, re-drill a rotor to use CB pattern, or swap front hubs.
If you seek improved braking, adding a dual disc setup is easy with stock parts, plus having the stock rotors drilled/slotted/thinned helps a touch. All depends upon what you seek, why, and your skills.
