No, because Davy Jones and JB losed to Imu. How exactly Xebec could know what needs to defeat Imu?
No, it's ruins the story. If BB kills Imu because he, for example, used attack like Pain, than and only than it wouldn't feel bad for story. But if you make someone like Madara beign defeated by Naruto not even at full power. Than this story tense will always be false tension. You should end this story immidiately,