Well, here's the thing. I'm not speaking from the ECP standpoint, but rather from the standpoint of someone who has learned alot about animations. Basically, there is no way to detect when a player uses the right mouse button to zoom in, or uses optics (well, AFAIK, but I'm 90% sure). So basically, it can't be done how you imagine it. It certainly would be possible to give the player access to a relaxed position in one way or another, but in the end it might not work very well.
However, for the weapon on the back issue, I do have plans to make a better alternative to that, although, again, this would be independent of the ECP.