He also modeled this today while I was at work.

All in all, I think you guys did a good job on its design. Everything seems to be in place and workable (from what I can see/little I know of flamethrower operation. One thing, though: I'm not much of a Pyro player (I generally prefer playing Heavy or Demoman), nor do I really have any qualms against the class, but I don't really see much incentive for "napalm" over compression blast. Explosions, possibly jump with or increased damage? I'd like it if you could elaborate on that intended mechanic, but the design itself looks good.

We were thinking that it would do more damage but consume more ammo, something along the lines of 50, as opposed to the air-blast 20, and to use the napalm it would be the same Mouse 2.

The smaller, narrower tank would be where the napalm would be stored, and it would still have the regular propane flamethrower with the larger tank. I don't know much about flamethrowers either, I think he does though, so he could probably elaborate a little more than I can. I'll have to ask him when he gets home.