Was talking to a Bike Friday employee and he mentioned that the trailer shop nearby his work, BicycleR Evolution, does custom trailer builds. He was saying a Burley Bee width trailer might have the very annoying tendancy to tip if it's top heavy and you bump a curb/rock or what.
A custom build frame would not only allow a wider wheel base, but might just need to be a simple s-bend with angle iron at the front and back to secure your table case and add a padlock or padlock bar. Also, if you have a bulky load, a Burley Bee style trailer often has a dropout-level bar/hitch and that limits the radius of your right turn, or what directions you can back your bike up. You might consider a seat-post level trailer bar/hitch which avoids that. (Might not help if you're planning on putting cargo on the top of your bike rack, tho.)

http://www.bikerev.com/

Hope your project is coming along well however its going!