Great video.
I've thought about getting a greyhound... and just making it run. But I can foresee the problem as the dog ages.
I'm working on rebuilding a home-bult longnose cargo bike, but hadn't thought of it as a dog hauler.
I'd probably leave the leash off once everyone gets comfortable with the bike. You seem to sop quickly if the dog jumps out, but it just seems like it would be safer to not have the leash.