Why not just mount a wide 1,000 lb. Eagle or Tommy Lift on the back
of the trailer?
I've used this exact same lift mounted on my dually flatbed to lift my LT several times, but I do have a 1500 lb. lift. I can load and unload it by myself. If I was going to use it often a small wood ramp positioned on the side would make it simple to load and unload straight on by temporarily unhooking one of the lift chains.
A wild ass guess would be $1.5K on the price - and they have optional platform extenders that fold over to give you an even wider base, but you won't need it.
You would no doubt need some stout angle welded to the trailer frame, a couple of extra leafs in the springs, and some offsetting ballast (an extra 100 gallon fresh water tank would be easy to mount) on the tongue. You may need to up the weight loading on the trailer tires for some extra insurance as well. The axle(s) can probably handle it with no problem.
The cable type (versus a rail type) that swings out and away would be ideal, giving you the ability to walk around the bike on the ground and facilitate easy tie down. A Condor chock and a few heavy duty ratchet straps would make it very stable and secure.
Just trying to think outside the box (pun intended)
using what you already have.