Purchased Overlays (like the MP Overlay) should be able to have defined custom areas (like Innovator) independent of the physical layout

Yes, it is something I asked long time ago, to turn the drum pads into full discs, but I got no answer…

I wonder what prevents to do it.
From the Sensel point of view I suppose it would not be difficult to allow it, and it will open a lot of new possibilities with the standard overlays.