It needs a hollow axle to set it up like they have it. I suppose it would be possible to swap out the existing axle bolt for a hollow one.
Then I thought it would work mounted to the paddock stand bolt holes. That was until I looked at the bike. I would not trust a trailer to the light welds that hold those fittings to the swing arm.
A simple hitch to the rear footpegs looks like the way to go. If you have a vertical-pinned hitch to the trailer that only allows swing movement, you only need one mounting point each side of the bike.
Take out the rear footpegs (I never carry a pillion anyway) and make up a block that fits in there with a horizontal bolt hole. That way the vertical movement is taken by the mounting bolt.
Bolting to the subframe gives the advantage of the bike's rear suspension to the trailer. However, the front of the trailer will fall as the rear suspension compresses, so the floor of the trailer needs to be high enough to cope with whatever movement the suspension allows the bike.
If you link to a hollow axle you don't have to take this movement into consideration. Another advantage of the axle link is in rough terrain. If the wheel bounces over a rock it will lift the trailer. Less damage to the trailer floor that way.
Here in Oz it would also need mudguard over the wheel, tail and brake lights, blinkers, the works. Here's our local design requirements
Luckily they don't have requirements for strength of materials or design etc. But they do have requirements for the hitching attachment. Gotta love the bureaucrats.
Funny thing is, there's no option for a one-wheel trailer. They assume two is minimum.