Can someone please sort out the Civil War thing for me? I'm not far into the game, but I'm trying to decide what to do next...

What has to happen for me to attack and defeat the other 2 Roman factions? Can I conquer all their territory without also going to war against the Senate? For example, can I unite Italia first and then take Rome? Is it possible to mod out the other 2 factions and/or change the requirements to attack them?

Same but for Senate. Are the requirements the same? Can I take on the Senate without fighting the other 2 factions?