You remarked that it was not proven that the head was completely recarved, or was originally proportional, and you go for the retouched idea.
While granting this as possible, i'm afraid I would still have to lean strongly (a full %80) toward an original proportionality and probable leonine features; I base this on the bulk of the images (anthropomorphic) of Eqypt's gods /god-kings. If Horus was pictured with a tiny, proper sized falcon's head on a proper, life-sized-scale human body, I could probably accept the Sphinx's current head as original. But, for the most part, ancient Egyptions did a rather good job of modifying the heads in their images to reasonably well match the body they were depicting attatched to that head.
The current Sphinx head, particularly if you remove the head-dress, is strikingly puny in relation to the rest of the body, and an original leonine head, (with mane, especially) would provide ample room for a full recarve, even is there had been significant weathering present.
I suppose we'll continue to disagree. Well, we will both get over that, I'm sure. Cheerio!