Yes, Exporting as a Catalog each time you wanted to Lock content would, clerically speaking, work. It would Freeze-In-Time current edits.
Regarding having never thought of the benefit of Locking, I'll bet you can finishing my sentence for me: It was when I had grabbed thousands of images from several years prior and had, evidently, brushed the 0 key on the numeric keypad. Months later, many Catalog backups later, I found that I had erased all Star ratings. But I had Deliberately done other stuff to those same images in the interim as well, so reverting to an old Catalog or backup traded one problem for another.
John Beardsworth got me through that, but there was a lot to it. Having been down that road, I got to thinking of just how much damage really could be done, giving the ease of selecting multiple files, and employing keystroke shortcuts - intended or not. So this is how I get to the vigorously help belief that we should be able to lock down portions of a catalog.
Thanks for your interest,
John Caldwell