OK, I'll go first. Nothing too fancy, the angled boards help guide the keel to the center of the trailer in crosswinds or when you can't actually see the trailer.
The box covers protect the lights from sun damage and breakage.
Assuming your boat has a tiller, and if you only need to move a quarter mile, have you considered sculling your boat? We once sculled a Catalina 22 about a mile on the Erie Canal when we lost the outboard. If you can pick a light wind day, or an on shore breeze, it's even easier.
First thing I would do is run a low stretch line between the two docks from the outboard dock post to the dock. Stretch the line as tight as possible and then hang two or three fenders at appropriate locatations. Then figure out the best place for a spring line to stop the boat before it can...