Looks fantastic man I love this idea the Pyro could always use with double everything :D

Pros: Lots of new idea implied to get the Theme of the Heavy Pyro Suit and you have put it almost perfectly there are cons which i think in my mind would improve the design you have in your mind just that little bit more fantastic.

Cons: If they are gas tanks on the back i'd like to see some valves and hoses coming out just to show that it is.
the suit it's self isn't reinforced which i'd like to see to make it suit the Heavy side of the idea

Improvements: Just if i was right about the tanks on the back i would like to see ajustment to show they are gas tanks and seeing the suit being thickend to get that Heavy effect
Not sure whats going on with the gas mask having the 3 breathing respirators i suggest just changing them around to make it not look so "Crowded"

Other then those i like this idea i just would like to see it when it's finished and some new parts added. goood luck fighting the audience

EDIT
Just looks at the screenshots more carefully don't worry about what i said about the mask