Yes that would work Norm , the 3 point linkage will allow movement from the quad bike .Four trailer jockey wheels would allow for height adjustment if you wanted any adjustments later on but as you said you can just set the height at one height.
Three point linkage would be more work to make than one trailer hitch and take longer to mount on and disconnect than having one trailer hitch but will work either way.
As we know the 3 point linkage adds traction on a Tractor by the implement adding weight to the Tractor but on the quad bike it won't aid traction .
Another problem with 3 point linkage is it can tilt 2 wheels off the ground if the quad bike goes in a ditch or over a mound but if it's flat should be fine , the problem is like a diff changing the pinion angle when the suspension moves.
Then depending how you set up the 3 point linkage you can get sway.
