If you have a visual representation of the boundary, using it in animation would become so much easier. You'd simply move the boundary bone out of the way and still see its effect. Each boundary line should have its own color, of course.
This would open a whole new world of opportunities, where you could create (cartoon) laws of physics based on bone actions.
BTW Here is the Moho file for the above animation: boneboundary.zip
I used my TransRotate script to dynamically bind the cursor to the rotating and translating child bone representing the cursor position, without rotating the switch layer that contained the cursor images.
