Jon,
I've sent you a private message.
FWIW, 'body snatchers' were always described as looking amusingly non-uniform, but I think the NVAC, like the Town Guards, at the start, looked entirely civilian and they felt very out-of-place and were too noticeable on the battlefield. Soon they seem to have purchased, or been given, or otherwise acquired, slouch hats and mainly khaki clothing. I think the NAM photo is at least 2 men of NVAC rather than infantry bearer corps because of their unsoldierly appearance (lack of helmets, belts, puttees etc) and because the pocket flaps on the jackets are non-issue. But irregular units like NC SALH, BMI, ILH did have more leeway with appearance... and the two men on the L and one just seen on R wear cavalry boots, one with spurs, and with slouch hats this suggests mounted infantry... so this could be, say, an SALH casualty being helped by his mates and NVAC; or perhaps it's his mates and the bearer co. of the SALH. The NVAC were a very fine bunch indeed.