Andrew,
Thank you very much for the reply. I was not aware of the new API and I will definitely look into that to see if I can somehow take advantage of that help resolve my problem.
I apologize that I did not explain the reason for wanting to do this; the countries where I will be installing this solution have very poor internet. We might be lucky to have a reliable 1 Mb connection that might have to serve 20 users for example. That is the reason we are trying to find a way to serve the 'multimedia-heavy' content over a LAN as opposed to pulling it from the internet. That is why S3 is not a viable solution for us.
I also understand that is might be simpler to install a series of small Moodle servers at each location, however we are trying to centralize student progress and authentication in the central server.
Any ideas are appreciated. To give a little more details, our main server is a robust HP DL380 Gen 9 with 10 SSDs plus a Synology NAS for housing the multimedia content (or the entire moodledata directory - depending on the final solution). The remote caching servers are additional Synology NASes. The Synology servers are basically Linux boxes with their own OS to simplify management.
Thanks again for suggestions.