Maybe if you aquascaped the tank so that there was a partition in the middle, like out of rocks and plants, so that each pair couldn't see the other pair all the time and thus feel more comfortable on their "side" or the tank. I would have a back up plan just in case.
Any ideas for other configurations? The owner of this tank would just like to have more than two of either one--could one have a single male and multiple females of the same species? Multiple males? Two pairs of the same species? Is there a different dwarf species that would work better?
I don't think it would be possible to have more than two of each, and I'm not absolutely sure two of each would work, either! I think you'd run into the same problems with two pairs of the same species as two pairs of two different species. If you could design the tank so that the pairs couldn't see each other, it might work, but it would be really hard in a 36 gallon tank. I also don't think one male with more than one female will work because the male will pair up with one and then the pair will harass the other female. Rarely do the rams spawn in trios. Your best bet might be getting all the same sex, but I'm not sure if male or female would be better. As to other species, I'm not sure. Apistos are SA dwarf cichlids but I don't know anything about them except that they are hardier.
EDIT: I forgot to mention that if you went with all the same species you maybe could have more than two if they were the same sex, but like I said, I don't know if male or female would be better. I hope that is clearer! (Sorry for the edits, I keep screwing up what I meant to say!)
You can more likely get away with more females than males in a large tank. With Apisto's I did well with Trios of fish...one male and 2 females....in that case the male had no territory.....but each female set up her own "homeland" and the male could go to either.
Also did ok for keeping fish, having 2 different species...only the docile species never got to breed....fine by me!!
My experience with the dwarf cichlids is that at spawning time the females are in charge. The most docile of them were Borellis and GBR's .
I had Cockatoos(3) and Borellis(3) in 55 gal. The males were perfectly polite to eachother... and as mentioned above the female cockatoos claimed each half of the tank as home when nesting.....therefore the Borelli females just had to avoid which ever side of the tank had eggs or babes!!!
So you could keep GBR's and Bolivians together as trios in a large tank with lots of hiding places and plants. ... and should over stress the fish.
I was never able to keep two bolivians rams in the same tank without major stress to the weaker until I had them in a 55g. They came from the same tank at the same time from the same store and still had issues. I could not imagine two pairs of rams, even of separate species, working.
However, all cichlids are different, some will be fine, others won't. I definitely agree with lots of territories and hiding places. Caves, plastic plants, anything to break up the line of sight will really help your chances of success.
Please keep us posted! Fins are crossed that it works out well.