Yes, the rebellion rate can be rised as you wish. I kept around a ridiculously rebellious 6-7 on average campaign once. The idea was that the computer would expand more slowly and surely (instead of spreading and collapsing) and it had been done successfully by other people with rebellion rates of three-four. My stat proved too much for the AI to handle, and the smaller factions were massacred very early by their own peasants :p
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