Erm, it's already there, well there aren't any skins, but you can modify damage and stoof in the script - add items into the crafts table in craft.lua and special effects on hit go into the hit hook in tf2.lua.
About team upping with mat5b - I would, gladly. Now go tell him the same
EDIT 1: A live preview of the backpack update here: http://www.youtube.com/watch?v=frtg4qqadHY edited 1×, last 20.05.11 10:02:24 am