Rather than try to fuck with the traces in the keyboard (irritating - only time I've ever successfully messed with that involved painter's tape and tin foil), I would either:
Solder the first solderable point from each button contact on the DMG board directly to other buttons mounted on the keyboard somewhere else - maybe you could remove an un-needed set of f-keys, mount a piece of wood or plastic there, and drill to mount some buttons - or just drill in the big open space at the top of the keyboard
-or-
cut away from the keyboard case at the bottom there, cut the front of a DMG in half and put the original buttons back in