Basically it is possible to extract the hdr's root filesystem (using humidify, and unsquashfs) to the HD's hard drive, remap a couple of the necessary folders from the HD's filesystem to the one now on the drive using mount (/usr and /opt specifically), link /media/drive1/videos to /media/My Video, kill the hummytv executable (preventing the box from rebooting using af123's additions for the webif), and run the HDR's one. Then copying to an external volume (be it real, virtual, or network) will decode the video as it does on the HDR
I've been meaning to finish streamlining the process, put up a proper "how to" for a while and post the scripts, but been rather busy recently... Hopefully finalise it all shortly...