I wouldn't try to add any more than two different species and I would be sure to provide plenty of plants, wood, rocks and hidey holes and I would look to add them together as very young fish. I think it will only work if you go with the non-aggressive types like I mentioned and do it with caution and be prepared to remove one species if the aggression gets to be too much and damage is getting done.
At one point I had my curvicep cichlid pair, my bolivian ram pair and a pair of angelfish too. It was world war 3 in the tank and the angels had to be rehomed. The rams were in the left corner defending that as their territory and curviceps was in the right corner defending that side and the angels just had nowhere to go without getting attacked