Would it be possible to, just like in the video, start a fire that slowly grows biger and stays for a couple of seconds?
And I'm not saying tauntkill, but the taunt should be deadly. By walking throug the fire the enemy gets burned with the same damage as your equiped flamethrower, damage measured by how far the pyro is from it's fire.
Also can you ad feul: people dying in the fire restart the burntime.