I'm sure someone has done something similar. i would build a ladder style frame from 1 1/2" round tubing that starts on the bumper and follows the curve of the trailer until it meets the tongue. you could attach objects anywhere you want and the weight
would rest on the frame, not the fiberglass
. you may need to beef up the frame depending on your load. The dirtbike on the tongue is easy enough, get a joehauler and cut off the hitch part and weld to your tongue.
speaking of mods, I cut the tongue off my trailer yesterday and set it on my flatbed today. I need to make the brackets to attach it tomorrow. I'm going to build a bike rack for over the cab and make a hitch receiver on the front of the truck to carry my dirtbike. i'm going to Alaska in a few weeks and have a lot to do. let me know if you need any help with ideas, I design and fabricate custom furniture for a living.