Some will say otherwise, but I say that any peacock will breed with any peacock.... and that's coming from me, who mixes a lot of stuff that others won't.
I'll give you a starter suggestion for multiple breeding groups in that tank. I'd go with a single group of each - start with 6-8 of each as juveniles and pull extra males as aggression becomes an issue. Pick 4-5 of the following:
-A robust peacock (manmade/linebred, jacobfreibergi, benga)
-Protomelas (Taiwan Reef, spilonotus, taeniolatus, etc)
-Open water swimmer/Utaka (Copadichromis or Nyassochromis)
-Blue-type Placidochromis or Cyrtacara moori
-Otopharynx (tetrastigma, lithobates)
-Maybe a Nimbochromis (venustus, polystigma or livingstoni - not fusco)
Given plenty of females, odds are that these fish will not interbreed in a 6' tank (though you need to still watch them).
That's where I'd start.
BTW, I have a bunch of fry/juveniles from a few of these genus. Shoot me a PM if interested.