I think we all do pretty much agree on the same thing which is this: If you have been able to maintain a tranquil state within the aquarium thus far, why risk it.
Honestly, I think at this stage, if I were to have convicts, the desire would be to merely have a pair breed and then feed their fry to the others. So I think I will hold off on the Convicts (or just raise a pair in my 30g(US)).
Keeping the aquarium the way it is works for me. I just feel like it could use a little more diversity regarding fish sizes etc... but due to the Jag and Festae being what they are, I do concur that it is very unlikely to find any smaller Cichlids that would withstand their aggression long term.
I am sure when they all reach adulthood the tank will look much more filled out, one way or another.
I appreciate the help guys! If there are any other fish (bottom or top dwellers) that others have had any success with Jags/Festae, please feel free to share!