In response to Chonaman, as Brandon says, this isn't a question of physical skill. Even if you set up the hotkeys to be in the best possible place, you won't be able to get off your panzerfaust remotely quick enough.
In MP with more than one player, just forget it. Battles lag so much you will be lucky to get Panzerfaust off once. You often have no physical control at all over a laggy battle once its begun, the keyboard is unresponsive.
I don't actually play much against the computer, I agree it is pointless. I was just illustrating the fact that the automated functionality is clearly there as the computer can use special powers multiple times simultanaeously.
I had heard the sergeant was initially too powerful. But, limiting auto is just an incredibly poor solution. It makes no sense given that aqua tanks retain their auto functionality. The aqua tank rush unbalances the game much more since it is an inexpensive unit, easy for UK to mass produce early in the game, whereas the sergeant is neither.
Also, the Russian commissar is very similar to the sergeant with its Molotov cocktail-throwing ability, and auto works for commissars.