Thanks for the quick reply!
I don't do as much development as I used to, but I could probably give #3 a shot.
Ideally, it would work only in /wp-content/cache/autoptimize/, and also only for Googlebot. (In case there ever is a problem with truly out-of-sync autoptimize files requested by a real user, I would still want to know of that).
There is a separate .htaccess file in the /wp-content/cache/autoptimize/ directory. Is it OK to experiment with that? That will work for experiments, but it's not a permanent solution.
It won't work permanently because, apparently, every time I update a post or page, WP-Super-Cache blasts the whole wp-content/cache directory. That's how my autoptimize files turn over so quickly in the first place. I can see new directories and new .htaccess file created at the time I update a post. But I can experiment with that file and let you know what I come up with.