We've been kicking around the idea of doing a Briareos costume to go with us "generic" ESWAT guys. Size is definately an issue, but only in height. Bulk can be achieved through the gear you outfit him with.
The trickiest part is the head, since it's the same width and scale as a normal person's, which makes for a mask or helmet to be hard to do, but we're working on a few plans for a head-sock idea with the armor plates attached to that.
Next year for AX 2004 we're planning on having a few different, more recognizable costumes from Appleseed in our arsonal as well, so I can't wait to see you guys there!
Me in my ESWAT gear at AX 2003:
You might be interested in some patches for your gear. We had some of these custom made. The insignia patch goes for around $8.50 a piece, but you can get a whole "uniform set" (Two insignias, vest patch, and BDU pocket patches) for about $20 total.
If you're looking for them, just let me know, because my embroiderer still has all the digitization done and can make as many as we need.