Wonder what they're doing to close the cylinder gap, otherwise that would be a bit spooky to fire in standalone bullpup mode, or even in master key mode with your lead grip placing your forearm next to the cylinder. There's gotta be something going on there.
Aside from that, looks like you'd need some long beefy fingers to work that trigger - a very long trigger pull, and probably quite heavy to rotate the cylinder.
It would be hella fun to have one to play with for a few weeks, just to see how it actually runs.