oh. and forgot to say about the making them more effective..

Perhaps change the mount of the chariot and its secondary stats?

Check under the "export_descr_unit.txt" file in the Data folder, and compare the different scythed chariots with the british light chariot - look at the Egyptian chariots especially. I can't figure out how they're different. Maybe just changing the chariot mount type to a scythed chariot will do?