the models arn't bad
the lack of skins isn;t an important issue (it's always a good excuse to allow those that NEED skinning practice to skin it themselves
)
the problem is poly counts. most of the models are a bit on the heavy side for a game engine. Example like the Thompson, the handles are too heavy on polys and you won;t see that detail of curvatures in the model unless you get it up VERY close into the players view.
Low poly modeling is about using polys to get the BASIC shape ( think siloette). then the skin fills in the details