well for the 3 main factions, the ones with additional hardcoded routines towards each other and the senate, I dont know how to trigger them, but afaik you need the Marian reforms before those kick in, and than A LOT of popular standing with the people ...
Getting them to trigger on an other Roman is rather easy, you need to make sure the Romans are allied (they dont cause outlaws if there wasnt any link between the faction, so an alliance between some Romans is a requirement), than when the alliance is broken ... outlaw the faction that doesnt belong to the "Roman Core" (hardcoded Roman alliance)
So you can have an outlaw-event at turn 1 (not turn 0) but it cant be one of the 3 hardcoded Romans ...
G
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