i would go with a all native tank. the florida gar a have is not aggressive at all unless it is a unsuspecting shiner lol. you could get some pumpkin seeds and perch and long eared sunfish. they have some great color. add a bullhead and that would be a great display imo. best part and afternoon on the lake and it is all free.
Gymnos require a cool down period & don't usually do too well without one - sucks I know. I've always been a big fan of balzani, one of the most uniquely shaped fish out there.
all the others are vanilla. Stein. Males look good females are bleh. Balzanii an Brasil's will either need to be top dogs or they might stress. Not sure if Balz's need temp drops or not.
But Winemilleri's are the best looking to me. You could keep a few things with them too. Even some smaller active wood cats since it's a cat setup.