I feel like we might get Dian eventually. (I'm actually surprised we got Anki before it.) Divine Wind would be interesting. It's better than the three we currently have, but you'd have to use Avian since there's literally 2 non-Fusion WIND Heroes. (The other being Stratos, who I doubt will ever be player-obtainable.)
The only masked heroes i think would be too powerful are acid, dark law, and koga (blast might be a bit too much, but at least he has low stats and reliance on avian). I could see the other ones getting added to the game at some point.