This looks great, Michael! I actually like this much better than typical gizmos found in polygonal modelers. It is the one great thing i always liked about Illustrator (I hate everything else about it!). Very interesting to have this in a 3D program as well... My only 2 comments are:

1. Must have adjustable pivot point (again, look to Adobe as example)
2. The corner handles look much too big
3. Must be able to do grid/object snapping as you drag the frame

jonah