One of the features I have found really useful at times is the persistence of the user defined zero point. The counsel of perfection for me would be where the user can define their own rapid movement points, with the same facility permitting the user definition of the Z axis, and that all user defined rapid motion points would all be persistent until explicitly changed by the user.
I would also like to see any user defined points appear in place of the standard compass points currently used on the rapid motion page. This would remind the user where they are going to rapidly shift the spindle, so the circles containing the compass points would probably need redrawing as rectangular boxes. An added refinement is to let the user define the rapid movement points from the page with the compass points.