That’s going to be a problem if you plan on becoming an official flavor. The technical board has taken the stance that flatpaks are not allowed in official flavors. The package “flatpak” is allowed, but flatpaks themselves are not allowed as they come from untrusted, external repositories. Snaps are allowed, but only if they meet certain requirements.
There are a number of rules you must follow to become and remain an official flavor. See this wiki entry.
Ubuntu GNOME was, as of 17.10, “absorbed” into Ubuntu Desktop. The flavor lead of Ubuntu GNOME, @jbicha, now works for Canonical on the Desktop Team. Therefore, Ubuntu GNOME lives on, but as Ubuntu Desktop. I’d be worried about brand confusion here, but that’s just my opinion.