In C6 there is more transparency options for shaders, In-Scattering; an effect by the light reflected by small particles inside a medium such as cloudy water or a smokey room and a direct Absorption control.

The DCG shaders do have some "3D shader"s for turbulance, noise and water.
http://digitalcarversguild.com/plugin.php?ProductId=18

I'm sure with this lot you could make a person look like smoke, I'm going to investigate those for my cannon smoke in the flea circus.