You should take a look at how AICC packages allow this - You would need to set your AICC packages up on your own server using some form of AICC content server hosting software (Moodle can't operate as the AICC server) and then you supply AICC Zip packages that link to the content on your external server for your clients to load in Moodle.
Moodle supports the playing of AICC content - both self-contained and external HACP content but cannot operate as the AICC content server.
I haven't done this myself and haven't seen any open-source solutions that would allow you to host your own AICC content server - but let us know if you find something as I'm sure others will be interested.