What you are asking for is to contradict a contradiction. The restless sleeper trait is gained as a contradiction upon enslaving settlements, you simply cannot contractict that. Even if you have a 'mean' character, he's still a human being and prone to have remorse for massacring thousands of innocent people.

There is no real solution for this, except having your armies led by captains or hoping your FM won't gain the trait. You cannot have it all

Maion
I don't know...

Can anyone provide a source that gives evidence that Hannibal, Ceaser or Alexander the great had a whole load of sleepless night due to the guilt they felt for the coutless dead they where responsible for?

Having guilt ridden, moral generals just doesn't seem to fit the mood of EB.