I don't believe you need to buy anything. I set things up a little differently than yesterday and I think this is a pretty good result. Here is what it looks like using a virtual MIDI cable (note: echo on in the MIDI track is not necessary):
I grouped two volume to group A and two pan controls to group B.
Added remote control to track one volume using MIDI CC2
Added remote control to track one pan using MIDI CC10.
Starting looping (the video actually starts here)
The volumes and pans are tracking the appropriate MIDI automation lane.
Change values in the automation lanes and the volume and pan faders respond to the changes.
Disable the remote for the first track pan and the group stops panning.
Re-enable setting the remote control to CC10 and the pan starts tracking again.