I won't give you a straight answer on this one because I can't.
When it comes down to it we know cichlids can be unpredictable, and more so when we're dealing with mature fish. Technically the Brichardi can work with the Haps and the Haps can work with the Front, but because you're dealing with mature fish used to their own space, any attempts should be made with care. It helps to add them at night, and some find rearranging rockwork can help too. As a safety precaution I'd hold off on re-doing the 20 (while you deliberate what you want to do with it) and keep it running in case you need it.
As far as the 20 is concerned, have you considered shell dwellers?