In Blood Bowl this isn’t strictly true - there’s whole teams with official rules but no models, like Norse, Amazons, Chaos Dwarfs and so on. Even teams with GW models don’t necessarily have them for all their players - there’s still no Blood Bowl Kroxigor and the Lizardman team was released years ago.
That said, I can see this being a Forge World release shortly after the Khorne team comes out, as Nurgle has their Forge World big guy with the Rotspawn.