If that does not exist, it should be a really great feature to make more complex animations easily :
For example; I have a switch layer containing all the frames of my eye closing. It's an image sequence, let's say I have 3 differents images.
Then I bind it to a little "controller" bone.
When I change the angle of that bone; the switch layer changes its image automatically :

It would be really cool !!!
The problems I see is that something should be done to make Anime Studio choose the right frame (for example; guessing which image to show using the number of images and the degrees of the angle; or a timeline of 360 frames for the switch layer, each frame is an angle degree...)
Also, there should be a way to use different images if the angle degrees are decreasing or increasing (opening and closing of the eye could be different).
...
I think we should talk about that but i'm sure this could be very handy !