Not a script, no
But a new unit addon, yeah

Just find a transparent texture, using O2, and apply it over the guy
Weapons will float, but it would look cool

But... The ai will still see you no bother.. Unless you do something in the config to change the units visablity (Look at the black ops config, it's in there, in the commented config files)
I could to the model (Would take a second to do), but I cant do the config

- Ben