Right, now picture that design scaled up and strong enough to carry a 700lb. motorcycle. Since the CG would be very high compared to those cargo loads, it would need 4 folding swing-out arms to give you something wide to strap the bike down to. The whole rig would be about 10 feet long.
I would have a plate for the kickstand to allow the bike to stand on its own while you rig the straps. Without it, you'd need one guy to hold the bike up while you strapped it. I'd want it to be safe for one person to do alone.
The only tricky bit I see is all those monowheel trailers have the wheel at the rear and in line with the hitch and bike, of course, and that's where you want to roll the bike on and off. Solution #1 is to place the wheel off-center which means the hitch point also has to be off by the same amount so it tracks straight. Possible, but I do not like this idea.
Solution #2 is use 2 wheels so the channel for the bike runs between them. It's balanced, safer if one tire goes flat, halves the load on each tire, solves a whole bunch of problems. You're thinking "that's just a regular trailer". Oh no, not if it's still only 18" wide. It's still using the universal joint hitch that doesn't allow it to twist relative to the towing vehicle. The stability comes from that, not by having the trailer's wheels 6 or 7 feet apart. It's still 1/4 the weight and width of a conventional trailer.
This makes it a trailer as far as the law is concerned, too. If your state doesn't regulate light utility trailers, no sweat. In mine (PA) it would need to be titled and have lights.
PS a quick check of trailer tire ratings finds me a single small trailer tire rated for 780lbs. that could carry the whole loaded rig with an average sized bike should one fail. That's a pretty good safety margin. Since the trailer can't twist you could remove the bad wheel and just keep going! Try that with a conventional trailer!