Yeah, that's quite a good start.
I wouldn't bother modeling the treads unless you're hoping to bake them into an ambient occlusion map and then remove them later. Only very large treads are modeled in the TF2 style (see the tractor wheel, possibly the dump trucks). I'd also dump the details on the handles for the same reasons. Most stuff like that in TF2 is baked in via AO or painted on.
Otherwise, what other folks have said -- exaggerate the proportions. Think of how big the TF2 character's hands are (they're HUGE) and imagine how people with hands that large would have to build something. Thicken up the metal plates, etc.