My solution is to build half-stack armies of only scythed chariots and use them to eliminate rebels. Chariots have cheap upkeep and they are extremely good in autocalc, so there's no need to bother playing out the battles and they will beat most rebels easily. I have 4 chariot groups roaming around my lands looking for rebels to kill. They got up to gold chevrons quickly and with gold weapons/armor they are now an unstoppable force. I never use them against non-rebels though.

As much as I hate chariots in battles, it's nice that they can be used for destroying those annoying brigands in auto