What's the tank size, how many fish, and of what type?
Personally, I would not recommend it. The Peacocks, no matter how robust, will never be at ease.. or reach it's potential. However, when I tried it, I fell in love with the Haps and Peacocks and eventually moved away from Mbuna(Small number of Mbuna can work in a 5' or 6' tank with haps, but I wouldn't keep haps or peacocks in with a lot of Mbuna, especially in a 4' or smaller tank.
That being said, I've done it.. I had a Lwanda that did OK. Jacobfreibergimay do well, Otter Point, my Eureka peacock is pretty mean. Bengas and other peacocks I tried tended to stay in the corners of the tank(benga, Stuartgranti, don't even THINK about a Maylandi or Kandeeses which would surely die.)
I had a Red Empress that did well, but he was hyperdominant and put the mbuna into hiding... which is not typical. ( I have video of him terrorizing zebras and Demasoni)
A nice sized Bucco or Champ may clear you tank of that pesky Mbuna problem too(that's a joke, being that I don't care much for mbuba, I'm not suggesting it)