It's a good suggestion, but I have to say, Firebugs don't need new and exciting ways to pick off small ZEDs, they were excellent at it before, and so is every other class. What they need is some way to deal damage or otherwise contribute to killing Scrake / FP (currently the flames just piss them off) and preferably do it without obscuring them from the team's vision.
As for the full helmet, I'd be all for buyable accessories such as these in order to add more depth to the game.