Honestly, I don't see any of the current women beating Rousey...she's that far above them in talent, training, preparation, etc.
IF you want to see Carano fight, let her work her way up (from the middle of) the rankings. At least that way there MAY be a market for her fights. Throwing her in with Rousey right off would be mis-management (and unlikely to even get sanctioned).
FALLBACK POSITION: Do a movie with Rousey-Carano, both of who have name recognition and who could plausibly anchor a franchise as good/bad gals tangling every so often (think Bond-Jaws as an example). It'd be more entertaining and more lucrative for both women.
Of course....I could be wrong.