Bravo! plus a small need for docs

I've been doing exactly this sort of thing for several years now, though only as an .htaccess hack + very short stand-alone PHP script.
One version of my version is currently bundled with my site wrapper project - You can see the stand-alone PHP caching-proxy script here.

I've occasionally wondered if it's worth taking the time to make a module out of it - however, as you've found, it is the sort of thing you configure per-server. Hence putting the file proxy config settings into the database variables table would quickly get clobbered if syncing development sites. :-/
So ... I see that putting the setting in the site-specific settings file is a good sorta compromise. Trying it out now (Have a site with 26,000 files that I just don't really want to mirror to my laptop!)

ANYWAY.
Can you add a copy of or a link to the INSTALL.txt to the project page? Just so we don't lose time poking around the UI to see where the new module appeared after turning it on?
I half expected it to be extending the admin/settings/file-system
I like the habit of adding a small message to the hook_enable alerting users where to go to enable new functionality, as we lose a lot of time wondering just where modules have added their bits. In this case there is no UI at all - but even that would be nice if you SAID so.
It WAS right there in the INSTALL.txt, so bravo for that.