[DonRotolo]

I can see it as possible. Breech-load from the top (balls just fall into place). Re-cocking the mechanism can't take to much time though - a second is a long time.

Whatever powers the slingshot needs to be highly repeatable - if you pull back X inches, the trajectory needs to be exactly the same, time after time, even if you have to replace whatever it is between matches because it broke or something. That's not an easy problem.

It appears that you are considering being able to "shoot from anywhere" - perhaps you might want to optimize the shot from one or two spots (distances) only. Otherwise this becomes a serious technical challenge - the mechanism must be built very precisely to have that capability.