Game Balance
"Wait," you might be thinking, "won't this ruin the balance of the game with tons of overpowered weapon designs?" Nope. The contribute feature is exclusively for model design. The TF2 team will take your submitted content and incorporate it into the gameplay in a way that makes the most sense for TF2. (You can submit gameplay ideas for new items, just like you've always been able to, by emailing us or posting them on the TF2 forums.)