The overwhelming majority of people who bought Mayweather/Pacquiao don't know anything or even care about boxing.
The best numbers UFC could hope to do would be anything with Rousey, since she is the one who draws non-fans of the sport (which are the most numerous and willing to pay money), probably vs Cyborg though Rousey's opponent is 100% irrelevant. Co-mained by Conor vs Aldo. Perhaps another title fight for the third slot down.
Even then it wouldn't hold a candle to MayPac numbers. I guarantee it'd be a much better show however.