I too lightly entertained it since I liked it flying Diamonds and I was installing the brakes for other reasons. It took less than 5 min of thinking to know as simple as it looks they’d be a lot of design to make sure it would be structurally and stability sound. I imagine that rudder authority, wheel locations and caster arm length/angle would need to be designed properly so it’s not unstable or unresponsive. It would also likely need engine mount modifications and add some significant weight.
The common Pipers/Cessna 172 have about a 30ft turning radius. Here it sounds like a nosewheel Sonex (didn’t see any numbers for the Onex) would be similar: