It is possible to mix species in the same tank (certainly happens in the wild), you might want to think about choosing species from the different lineages and keeping small groups of each species though to rule out the small risk of hybridisation. Key to this though will be the size of your tank.
I currently have a stock tank (juveniles) with Apisto bitaeniata, Apisto panduro and Apisto juruensis, and another tank (adults) with Apisto norberti and Apisto agasizzii with no problems.
Certainly for me, the key is to make sure you have species with different body shapes so it is easy to identify the females of each of the species