i would say that a 16 gal would be far too small for N. leleupi (lemon cichlid) because to get a pair you would have to have a small group and let a pair form up and remove the extras, and in a 16 gal. you would end up w/ the stronest leleupi killing everything else. Then even if you were lucky enough to get a pair to form up and got the extras out before any deaths the males are so aggressive to the females that you still could end up losing the female. I have a breeding pair that owns half of a 55 gal. And i still have to keep an eye on the male, and that's w/ pretty much all the caves in the tank being made so only the smaller female may enter.
Now onto the brichardi complex. I have heard of ppl keeping breeding pairs in 10 gal. tanks but i prefer to go for more room than that. I currently keep 4 N. pulcher "daffodil" in a 45 gal. tank stacked to the top w/ rocks. So unless you have a definate pair and have a place to move them if things get out of hand i'd say no to the brichardi also.
I think that shell-dwellers would be the best path to go down. And no i'm not just saying this because shellies are by far my fav. fish

a 16 gal. would be good enough size for a pair of any of the more smaller shellies, some of my favorites being.
N. brevis
N. ocellatas "gold"
of course N. mulifasciatus

Which you could have like a male and 2 fm's.
N. caudo.
and there are many others too
you could also get away w/ a pair of smaller julidochromis like transcriptus or possibly ornatus, but both of these are EXTREMELY same species aggressive to others not in a pair w/ them and since they are virtually impossible to tell apart by apperance you would have to start w/ a small group and that just wouldn't be good in a 16 gal. peace................