Magussen: You can remove the super-faction and sub-faction lines. As far as I know the result will just be that the Senate will behave like any other faction (i.e. it will make war on other Roman factions and expand). That might get messy if you leave the Senate as is - because they get nothing but Praetorian units in XGM.
What difficulty level do you usually play on? On H and VH I have seen the Carthaginians, Gauls, GCS, and Macedonians attack Roman settlements (I don't remember with other factions). One thing that has bothered me is that the Macedonians seem unwilling to attack GCS settlements, even if you start the game with them at war, and will a huge army sitting next to a lightly defended settlement.
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