I realize that there aren't currently any specific controls exposed for any of the animations, but a common motion style is a slow push on a graphic or text. If we could define a starting value for the Zoom animation (ie, 80% or 120% instead of the current 0%), then it could be used to composite this effect live. The end of the animation would be 100% zoom, as it is now.

In practice I'd combine this with a Fade TransitionIn and use positive or negative values and a long Duration to get a push or pull.