Okay, so you all know the issue with "Dances with Wolves" and it's SF evil twin, "Avatar." The short hand is, "White man arrives to save disadvantaged but noble savage/magical negro community from complete annihilation."
What if, for an invasion story, humans became that "noble savage/negro community" but couldn't win until one of the aliens (or a group of them) defect to help them. Only slightly covered by many stories, but in those cases it's mostly "alien gives human the key to winning, mostly unwittingly." Or the "two alien species fight for Earth, one species realizes it won't win unless it co-opts the humans onto their side." No no no. Do a full on alien goes "native" for their love of the "simple/magical" life that is being a human, and leads us to victory against their own race. Add in a romantic "human" interest (for double bonus points, make the alien nominally "female" and the love interest a guy, and "she" has to convince him, no Capt. Kirks boning anything green and in a skirt).