Oh, yikes! As an old-time HL/Source engine user you’re givin’ me nightmares. Using “make hollow” on anything more complicated than a cube would definitely produce hideous unusable soup that those engines wouldn’t know what to do with (and you wouldn’t want 'em for Unreal either). Might even crash Hammer/Radiant.
An actually-good version of that tool that produced a decent mesh could be useful though, sure - though like somebody said, you’re usually just as well-off just flipping the faces.