I'm assuming that there is no real way around it, but during the imperial campaign, what happens if you accept the senate's request that your faction leader commits suicide? Will he go through with it? Will the senate ask you successive leaders until you disagree?
In Rome Total war, your leader is in fact a hero you can control (usually the most powerful since its the first one you get). When you choose to kill him, he dies so you lose that powerful unit. Eventually, the senate will grow weary of you again later on and will ask for another suicide until you rebel.