honestly...the best answer id give anybody...whatever fish you decide to put in this tank there is always going to be a tank...no one in here can give you a definite answer yes or no...Unfortunately with cichlids they decide whether or not they want to get along with the fish you put in the tank...And the other thing that sucks, is they might get along in the beginning but you have no idea what could happen when they all grow just a little bit more (maturity is a cruel thing).
So tread softly when deciding what fish to add...youre ideas aren't bad at all...the only thing to keep in mind though once you introduce the same species of fish you run into small issues
you could potentially introduce the same sex fish and they get aggressive and territorial (alpha male chest flaring), you get the opposite sex, they pair off and then they try to breed. this leads to territorial issues, aggressive breeding behaviors (nest guarding).
Check out some festivums, some of the smaller species of geophagus species are nice and pretty!