In my humble opinion the way to get round the Fanatic problem, show they are 'Fanatic' and still keep it real is, well, keep it real.
When troops go into a fanatic state as they have through history with Irish/Scottish Galloglasses Viking berserkers, most VC winners etc. up to and including modern day suicide bombers they are out of effective command and control.
Therefore in CM you could have a Fanatic indicator appear at the relevant time for example: The death of a commander. This could induce a fanatic state almost as often as a rout, but at this point put the troops into the same control state as for panic.
This would mean you could enjoy watching your Green blanket stackers and cooks take on the might of the opposition but could not use them in an unrealistic way. Once out of contact (if not wiped out) the troops would return to control but would Knackered and not fanatic anymore.
It's just like Saturday night fighting if you ask me, you never know which one of the idiots in the pub is going to flip and pick up a bar stool and when he does there's no stopping him. (Except with a good stout pool cue) Lol