Here me out. Aliens are cool. Star Wars has lots of aliens, but I'm talking the human ethics don't apply sort of aliens. The kind you can have a conversation with, but your values never match up. The sort that you can't talk down from what they're doing because the beliefs you have just don't match at all. War isn't ideological, it's a fact of life sort of thing. Life and death aren't a beginning or end.
Canon, Fanon, it doesn't matter to me which aliens are used but if you're wanting that fun alien extraterrestrial threat, hit me up. I'd love to get something proper going with this with other likeminded folks who've been itching to go full nonhuman sentience.