A nice idea, Wade, and there's a chance it'll return the audio to something close to its original state. There's an equal chance it won't. Let me introduce the concept of "mono compatibility" to the discussion. There are countless articles on the Internet about it which you might want to review; in short, what it means is that, depending on exactly what was done to the signal in order to "improve" it, remixing it (folding it down) to mono may not result in the pure mono signal that you started out with. It can leave you with weird phase cancellations, comb-filter effects, and all sorts of other unpleasantness that wasn't there to begin with. This is why hitting the mono switch was never a reliable solution in the era of the "reprocessed for stereo" LP.
