I sell whole birds, but only because I process myself and that eliminates the regulatory hassle. Selling cut-ups, per pound, requires inspected processing and a meat handling license.
Since you are using a processor, I see no reason why you couldn't just have a certain percentage of your birds cut up, and get a premium per pound on breast meat. When selling boneless/skinless breast per pound, you should be mostly paying for the rest of the bird. If you do the math on grocery stores geting 89c/lb for whole chickens and $4lb for boneless skinless breasts, you realize you're better off buying the whole bird.
Should you get stuck with the quarters, you'd be doing so at practically no cost, so why not? Any of those you happen to sell are your profit, and what you are stuck with comes off your grocery bill. There's more ways to cook these than breasts too, I've come to prefer quarters to breasts as the crock pot, smoker, grilling, baking options are endless.