I have a couple of Fatboys and a Jumbo Fatboy. While I do not use them for a camera bag, I suspect that it would work. One consideration for me would be the lack of padding, i.e., the camera in the main compartment would be subject to whatever knocks and bumps the bag receives during use. I think that you could probably get an SLR with lens in and out of the main compartment without much trouble.
A concealed weapon of small to medium size would fit in the zippered compartment that lays closest to your body, but again there is no padding between it and the camera in the main compartment.
I use my Fatboys on field trips with my progeny, trips to amusement parks, etc., and use the Jumbo as a bugout type bag in my vehicle. They are very useful, and would work with a camera, but the padding issue is something to consider.
Peace out.