I know it's designed as a cosmetic but if you had the skills to animate (which it looks like you do) this would make a great taunt. Something like the Engineer gets it out, winds it up a couple of times, places it on the ground. It proceedes to walks a few circles for a bit and then falls over on its back to end the taunt. I know that's not what you intended but I believe it would be a great taunt and I know if it made it into the game (as a taunt especially) I would have to buy it.

Anyway that's my opinion on the matter however it does look great as a cosmetic and I'm sure it would be a great addition to TF2 either way.