Well, not sure is the Pioneer LD-V8000 is compatible at this step of the Dexter development, but I would be glad to help them in any way to make it work with the Galaxian3 hardware.
But there's the sync singal to figure out between the 2 LD players...
Or maybe this could be solve if the Dexter setup would only run one 'virtual LD player', who could display the entire picture (Left & Right footage side by side)?
This trick (displaying one entire picture instead two pictures 'side by side') could be also used to emulate the game in mame...