Oh but there is...:devil. It just involves taking the board apart, gluing in a 3D-printed piece of plastic to completely fill the large hole to make it level with the top board surface, and then attaching a 3.5" lazy susan with 6" aluminum footpad disc to the new plastic piece.
Which I will eventually show when I finish my HC board...
If you're a prop maker, there's always a way. But we're talking about the average buyers of my upgrade kit. I wanted to make the attaching of my kit as easy as possible.