It is a little outside the scope of the ladder trailer, but I recently built up a homemade trailer from an old Burley kid trailer. You can usually get these really cheap on craigslist, especially if the fabric is all torn up. Then, you have the frame, wheels, hitch, etc. in one place. For mine, I stripped off all the extraneous tubing that was used to support the cloth part. Then, I had a bunch of 1x1s (boards) in the garage, so I cut a couple, put them across the frame, bolted them to the frame in existing holes, and then mounted a large rubbermaid type bin to it using some bolts, washers, and wingnuts...I got the more industrial yellow/black on from home depot. I've been thinking of making a flatbed for it that I could take on/off using the wingnuts but haven't gotten around to it.
With this set-up, you are limited in size of cargo to what fits on the old Burley trailer. I did recently see someone hauling a canoe with a modified ladder trailer. Good luck.
I did a similar thing with an old Burley, too, but I used some plywood I had in the garage to make a bed and left the cage to strap bungees to.
I have T nuts and some bolts holding the bin on, but I can remove it easily if I want a flatbed.