Since health matters are confidential, do we not run the risk of inviting people from the same area who may know one another and who may not be comfortable talking about private personal matters? The same thing happens when family members get together for a therapy session. When certain family members exhibit more serious problems, the other members accept the feelings of isolation that person might have.
In my view, the safer thing to do would be to invite people from different regions so that they feel comfortable talking about themselves and don't have to worry that some other veteran from their area may recognize them. Perhaps it would be wiser if the witnesses were strangers from different parts of the country.