The original plan for Kevin Owens upon his return was for him to be a face for a while, according to the Wrestling Observer Newsletter. Before his return, WWE aired a few vignettes with him bowling, going to the movies, hanging out with his kids, etc. which were meant to bring him back as a babyface.
There was originally no plan to have him turn on The New Day. That decision was made after Daniel Bryan went down with an injury at WrestleMania (his status is still unknown). SmackDown is light on the top heel side, with the only other option for Kofi to feud with pretty much being Randy Orton.
Daniel Bryan was originally set for a rematch against Kofi Kingston at Money in the Bank.
When Big E went down with a knee injury after WrestleMania, WWE came up with the Owens/New Day turn storyline.