I like what they did in The Ancient Mediterranean mod (TAM), which was to give chariots a huge penalty (like -80%) to attacking cities. I really don't like how powerful war chariots are in their current incarnation.
Perhaps, since chariots are very terrain sensitive, giving them -50% attack against cities, hills, forest, and jungles. I feel like this would balance them out much better.
I also like the idea of adding collateral damage, and dropping strength.