The issue with these "Let's give knights a way to piss off/hurt/damage the income of their lord" is that there's currently no reason at all for a lord to take on knights, other than to help the realm. Having knights does nothing for a lord whatsoever, and in most cases actually reduces the amount of gold they get. So if knights start banding together to hurt their lord, he's just going to boot them all without a second thought.
