Okay so I've changed gears. Thinking the SpyCrab is a bit of a novelty and not really fitting his character I've decided to go with a different class and theme.
I'm going to do a Chef Pyro with a hat and two melee items and perhaps a primary replacement and misc item.
Hat - The Sous Chef:
Melee - Rolling Pin:
I'm also considering doing an Apron for a secondary slot or perhaps the Misc slot.
Another thought is to do a wide angle flamethrower based off a gas stove and some other kitchen related nonsense. My thoughts are it might make spy checking easier or fighting a group of enemies.
I figure the melee weapons could have different health related effects either healing the pyro with each strike or buffing his/her max health.
END OF EDIT
Old idea of doing a crab themed kit for the spy. While I might continue working on this idea it isn't my main submission anymore.
If I finish with the Pyro gear early I might return to this later. Until then enjoy this slightly darker text.
I'm creating something I'm surprised the spy doesn't already have, a Spy Crab kit.
I'm replacing the Melee weapon with a Crab Claw, adding a new Eye Stalk Hat, and Crab Walking Spy Watch.
Since there are both red and blue crabs in nature the TF2 color palette works nicely.
I'll post more as I make progress on the idea.