I have to disagree with you again. It's IWIM since we heard the "yeah" yodel reminiscent of IWY. everyone has been all over that song. Really the great part of the song is that. Actually no for me it starts when sings "oh and I all I needed was a little.. " I always skip to that part. I feel it.
I'll go with WARRIOR. I really like IWIM but I guess that the album cycle started with her Struggle against Lyme and Warrior closes it perfectly. Like Goodbye closed the album cycle for Goodbye Lullaby. I don't know why but from Let go, except for Avril Lavigne self-titled, her last tracks always represents her more vulnerable side. I may be wrong but she's excellent at choosing the closing tracks for her albums!
The rumor is that they’ve been shooting footage throughout the era for a Warrior video, so I’m guessing this will close the era. Sort of like Goodbye, despite not being an official single. Warrior likely won’t be a single but she will release a video with footage from this era of getting her life back, being onstage again, doing fun events like the award shows, Hustlers premiere, racing thing with Jay Leno, shooting videos, etc. It would be a nice way to close her first era post-Lyme.