I have seen the Yak and B.O.B. trailers for bicycle.
I saw the Tagalong for safely having a child ride with you.
http://www.rybabikes.com/tag.html
I wonder if a fellow handy with tools might make a trailer rather like the Tagalong but without pedals, handlebars, seat etc ; and use it as a pack horse, so to speak, to carry several packsacks, or panniers.
Any ideas?