Here's some thoughts. Most any dithers will work, so long as they'll get big enough where he can't eat them or they are expendable. I'm not sure what your end game goal is, but it will likely be harder to keep cichlids with the gt based on how long he doesn't have any as tank mates. If your goal is a GT centerpiece with a bunch of dithers then you probably don't need to worry about his mean streak. You could pretty easily run male only convict tankmates, a sizeable GT will be able to beat them up just enough that they are like dithers, and the convicts shouldn't have a big problem with the GT if they have a place to hide.
Those anubias make for a very nice display, I am hoping we can see this tank after the anubias has grown for another year and your GT becomes a giant glass banger.