Obstinate Senate

[Omanes Alexandrapolites]

Hi and welcome Khanny!

Any idea if those conditions apply to the other two Roman factions or only the player controlled one?

Yes, they apply to both AI and player. However, the AI infrequently will start the war straight after the option has arrived, which gives you a short time of preparation.

Also, are there any other effective ways to piss off the senate apart from failing to do their missions (have been doing this for quite a while) and attacking factions they like?

There are two alternative ways of dropping the senate's love for your faction other than ignoring them. You can send the generals that provide bonuses for your senate popularity (see their traits) on a one way trip into enemy territory to rid yourself of their bonuses or, alternatively, you could gain as much popular support as possible - the senate hates a man who is loved by the plebeians! You can increase this rating by winning the majority of your battles, everybody adores a hero, and conquering plenty of territory for the glory of Rome! Also this tactic could work in the opposite direction by providing you with a high enough popular standing to begin the civil war without having to refuse senatorial demands.

Hope this helps, good luck, cheers!