Richie - an excellent idea!
What about just cutting a hole big enough for the cabinet, pushing the detector from the bottom so the only the cabinet is visible? We would have to figure out a way of holding the detector in place under the layout - maybe duck tape?
Did some thinking on above - it won't work. With the thickness of plywood and homasote the top of the detector won't show above the table. As you stated the detector would need to be taken apart and rewired.
The problem of the detector not being high enough also plagues my Z-Stuff detectors. They need to be raised also.