I think it looks too futuristic for TF2. The cartoony aspect is there and working, but the "theme" of it doesn't suit the game's time period or the character it's for at all.
IMHO, something similar might work, but only if it looked more cobbled-together like several other weapons. As if it was made by duct-taping and bolting a few household objects together, perhaps. Like, say ... make it powered by a car battery on the handle, make the handle look like it was very roughly ripped from the standard shotgun and shoved together with this other stuff, put that gauge on the handle as a separate piece taped to the side, etc. Giving it that homebrew look might help it fit in without having to totally rethink the design (you could keep this basic silhouette, but replace the parts with household objects such as pipes and the things mentioned before).
As it is right now, I honestly feel like it might be more at home on
The Jetsons.