The Flame Thrower is the human team's choice against small aliens and tightly packed structures. Here's the concept by alex_bo:
The tank will double as our incendiary grenade, so it should be a seperate mesh and have a (smaller) texture of its own. If it hasn't been attached to a flame thrower, a player can activate the grenade by pushing the button with the fire symbol on it deep into the casing.
If you choose to do the animations yourself, here's how reloading is supposed to work (note that some of the detail work is outdated):