I love animated sky
. Sky is really something I enjoy doing. I agree with you we should have a way to animated the sky.
Currently there are several issue, we can already do clouds moving to some degree, but separate from the skybox.
It's also not easy because we use the skybox for other things (like image based light), so it might not be easy to modify the texture. For the sun we are currently working on it to be able to modify with a script.