I would really love to see the option to be able to send a peace offer to the AI.
off course they don't always need to accept, they can have a set of parameters for it to accept.
If they are on the winning hand, they don't need to accept off course.

But, at the moment in COW with the missiles and long range weapons. It is hard not to have a few days without combat.
So just resetting your status towards them to peace, and wait a few days just doesn't work. And you'll end up in an never ending war. Or you're forced to annex them completely.

but this is off course just my wish...