How's about Avengers 2 opens with Namor attacking the surface world/NYC and SHIELD has to fight him off. Then, as I've mentioned earlier, Carol Danvers has to reveal her true self as a Kree spy/Earth sympathizer and save the day. Later in the film it could be revealed that whatever pissed Namor off was part of Thanos' plan and he could join the Avengers (with Ms. Marvel, Falcon and War Machine) and possibly some GOTG for the final battle.
I know it won't happen, but think it would be cool. Just speculating.