Well, I have never heard of or read about stakes being planted in the ground behind a gate, but that doesn't mean it was never done. In any case, gates in MTW 2 are pitifully weak. I mean, there are no barbicans, no murder holes, only one portcullis in the passage rather than 2, 3 or even more, no drawbridges, etc. Charging through a gate should be damn near suicidal, so I don't feel guilty about putting stakes behind them.