Well some of the more common sales for Cichlid's I would have would be - Angels, Discus, Rams, Oscars, Firemouths, Green Terrors, Paratheraps, Convicts, Texas, Keyholes, Apistos, Jack Dempseys etc... But if you are looking for say 12 unique or 'bigger' species I would consider: (some you have already listed)
Managuense
Motaguense
Dovii
Uaru
Festae
Trimac
Midas
Salvini
Buttikoferi
Electric Blue Jack Dempsey
Chocolate
Ornatum
I think having these Cichlids in your store would be adequate for most hobbyists. Lots of color variety and some of these species you just don't find in your average LFS. Pike Cichlids would be great to have and also, be sure to have certain miscellaneous species of fish that are unique and can possibly be compatible with some of your selling stock. (Prochilodus, Bichirs, Barbs, Loaches, Knifefish, Catfish etc...)
Overall, the best way to ensure sales is to have a variety of species that Fishkeepers of all experience levels and tank sizes can choose from. Best of luck with it!