Banjo cooker in the wood brewhouse question

I'm getting close to having my brewhouse liberated from the "shed" title that it once served as, and had this idea....(brief visual of the brewhouse: approx 75 sq ft trapeziod shape, 2x4 stud framing with OSP panel walls inside and pre-fab siding panels out...regular tar shingle roof)

In one corner of my brewhouse I was thinking of putting in a 3' x 3' semi square brick "tub" about 3.5' tall (almost to the top of the BK) to use as a hot box for the banjo burner. I would have a exhaust hood, and only burn with the fan on, window and door open. The upper 2 sides of the square where the walls are would be sheet metal covering the wood above the bricks. I do not think that there could be any fire hazard, but there always is no matter what. I saw a mini version of what I am thinking on one of the beer porn-180 brew rig threads once, but up on a stand.

Has anyone done something like this or does this just sound like a bad idea?

Thanks

What part of the country are you located in? Could you just put in doublr doors leading to a porch/patio and roll the rig out to brew? If not, I think the steps you mention above would be ok. Or you could switch to an all-electric system (keep the hood).

I'm just north of Seattle. Not a really dry area
I found a picture in a link of a larger version (sort of) what I'm thinking.

http://www.bluepointbrewing.com/brewery.swf


I would brick and mortar under the burner and build up from there with open access areas for the gas line and lighting access. The top would just be open and I'd use my BK lid instead of having a nice dome. Then above that the sheet metal and exhaust hood.