If by "I have looked to do this" you meant modding, there are some values in CoreAIDefs.xml under "RELEATIONS" (sic) you can change to mostly do what you are asking. Set the values for opposite alignments (early, mid and late game) to like -30 and everyone on opposite alignments will always completely hate each other. It wont be war 100% of the time, they will occasionally ask for peace, but they'll declare war again a few turns later, and there will be no chance for any sort of treaties or collaboration. In that file you could can also make it so everyone hates each other, regardless of alignment, for an all out FFA war.

A permanent war option would be nice though, not really my thing. but I know it's fairly standard for the genre so I'm sure many people use it.

Would ruin diplomatic victory if required, as well as make diplomacy almost useless in general. But I agree it could be a fun option. 

This would be a nice option. And would be better if you can set it for each empire without having to mod it in. That way you could set up a bad guy or two that cannot be reasoned with that woulf be your main enemy in the game.