removing a permanent offset from an animation

I have a number of animations imported from mocap data, at the minute they're all seated poses and so the root doesn't move much from where it sits. However, unfortunately they're all at some arbitrary offset from the origin due to how they were captured.

I can either measure the offset by hand and compensate for this, or recenter it every frame using a call in lateupdate, but this won't scale particularly well. What I want to do would be something like this:

Extract the animation curves for the root node translation. Define the offset as the value of these curves for the first keyframe. Remove the offset from all frames in the curve. Reapply the curve and save the animation.

I'm aware that Unity 3 seems to have the functionality to do this by deriving from some of the editor classes, is this actually possible/worth doing?

Thanks