Well... I haven't left the scales off and used the knife w/o them, but I have removed them for cleaning/lubing.
I would think that the knife would be nearly useless w/o the scales. It would be very thin side-to-side and probably way too flexible. Worse, it would have almost no handle thickness top-to-bottom so there wouldn't be anything to hold on to.
Everything would probably reattach to the liners w/o the scales, but you'd have to shorten all of the screws as well as either shortening or replacing the pivot.
Having tried to use a BM 707 (and failed because of the handle's thinness), I'm pretty sure a D4 or E4 modified this way wouldn't be useful to me, anyway.