So-Cal Tear Drop Trailers offers side mounted 1 1/4" receivers on their trailers.
They mentions flag poles, cocktail tables, umbrellas... Here's a link:
http://www.socalteardrops.com/options.php?cid=1&oid=5
There is a grill that nounts to a receiver too, can't recall the brand.
In the two photos you provided, the receivers are both 2". 2" receivers have advantages over the 1 1/4" receivers. All else the same, there is less wobble with the larger receiver, which might make a 2" more suitable for tables and stoves...
On wobble, the very best anti rattle/anti wobble/anti tilt pin I have used is the J shaped Drawtight pin to the right in the link below. It requires a second hole in the receiver tube but gets rid of all wobble. I use them and use my UWS receiver mounted carrier with a piece of plywood as a grill/stove table and its stable as can be. I fact, I can stand on the carrier and shift my weight without it moving.
http://www.etrailer.com/comparison.aspx?pc=13613&pc2=63201
When I was considering bulding my M101A2 for comping I had planned to incorporate a couple of side mounted 2" receivers, welded to the frame and bolted or welded to the tub for the same purposes you're looking at.
One thought I had was to install two receivers per side forward of the wheel wells which would accomodate larger tables work surfaces and solve any tilt/wobble isues as well. (My M101A2 has the wider A3 drop axle and the A3's 12.5"x37"x16.5" tires, which extend past the edge of the fenders, so spanning the wheel well was not an option. I think it is with the A2 axle, wheels and tires.)
JPK