For me, to make it more challenging, I would do this:

Set camera to be fixed on the general in the options
Do not pause during battles
Do not save the game at all unless you have to stop playing
Play on VH/VH
Pick one general and only when he fights do you go to the real time battle map - otherwise, you autocalc other generals' battles for the realism of not being there.

Just some ideas
Mebbe use this in combo with the other posters' ideas

John6305