I think this shouldn't be added. I personally think we don't need added complexity to the AvatarState. Like
@Simplicitee said, it limits what you can do. For avatars, this limit wouldn't be comfortable to the long run. AvatarState is fine as it is. Players can bind moves such as ElementSphere and SpiritBeam, and it would be good to go. Also, there are several addons that allow players to do these things in the AvatarState described here. I'm just saying... no hate please. <3