I takes like 10 seconds to think of some good stats relavent to the item in question. Hardly a waste of his precious time.
Anyone can come up with bunch of stats, but ones that work ingame well and impress valve enough to add them is whole different matter, there is tons of different suggestions for weapons all over Steam Forums and other places, yet it has only happen twice in TF2's history, if making idea that Valve actually decides to make weapon is 10 seconds matter, how come it has happen so few times?
Look at Swordfish idea, on paper it sounds good and doesn't take much time to come up with those stats, but when we start combining it with different weapons, the item might be too good. There is a lot of different variables in this game, building good weapon in your head that is balanced is not that simple, and by the end of the day, Valve probably won't like it.
He can try, but it is better put focus on making the model.