To me, a proper hitch and attachment system would be the most important factor. I've seen videos on YouTube of people towing a wagon with a bike using rope (not a good idea). Of course, I've seen others of wagons being towed flawlessly, and I've asked how they hitched them together, but I never get a response...

I'd love to tow a wagon if I just knew exactly what to do. Chances are that both the bike and the wagon would require some sort of custom work.