This is screaming for a widget in Chilipeppr for fields for the width of the plate and the width of the bit and then have it automatically probe each direction for you and do all the zeroing. This can be so helpful if you are working with stock that has rounded corners.
I would love a widget inside ChiliPeppr for something like this. The widget should let you auto-load the gcode to actually mill out the shape. Then of course the widget should act like the Touch Plate widget and give you all the goodies to actually run the process and watch it as it goes including stopping it in the middle of it if there’s a problem.