I think it could work. However, watch out for the JD in case it gets territorial and chases the other 2 cichlids. To be honest, my mental picture of a 75 gallon with only a BP, a JD, and a female convict doesn't look that visually appealing since the tank only has 3 cichlids. The other problem is that you don't have enough fish for the JD to spread out its aggression.
I'd suggest removing the JD, and building your tank around the BP and convict that you already have, and adding some other smaller-medium sized fish that are semi-aggressive like a school of tetras/barbs/livebearers. You can also add other medium-sized cichlids like rainbow cichlids, more convicts, blue acaras, etc. Or you could also try a shark in there or gouramis too.