Cool, but a very niche market. To begin with, only 3% of the U.S. rides a bike, and I'd say of those, maybe 5% ride with a sidecar. And without an Earles fork, sidecars are somewhat difficult to steer, making them less desirable.
But still cool. I built one once, for a CB125 I had. It was for cargo only(because it was only a 125!), but I did have thoughts of convincing my dog to go for a ride in it. He wasn't too keen on the idea. He always barked at any bike I had when I started the motor.