I'm no 3d modeler guy, but there must be some parts of the 1942 soldier that illustrate wth I mean..
Basically...take the current soldier, and just 'pull out' the costume. That will make him look like he's wearing more 'layers' of clothing. To give the illusion of a jacket or say a jersey thats kind of baggy at an edge...lets say the bottom of a jersey top...go around the bottom edge and pull it out from the rest of the upper body. Then make a new set of verticies(? I think?) below that, and set it into the body. That should give the illusion of a heavy/baggy jersey over regular clothes/body. Maybe I should make a picture, lol
EDIT: EPIC PAINTBRUSH SKILLZZZZ
EDIT edit: apparently thats too much work. Then you're gonna have to shade your textures. I think. lol. Pretty sure thats the only way to give the illusion of bagginess without changing the ske, as u says.