#1 Samoa Joe
Samoa Joe was definitely WWE's best option when it came to replacing Roman Reigns. Joe is said to be ready to return now after a lengthy spell on the sidelines due to a knee injury and is rumoured to be playing a part in the main event match anyway.
The confusing part would be the fact that Joe did walk away as a heel and he would be returning as a face, but considering the fact that Joe perhaps has issues with just about every person in this match, it would be interesting for him to try and gain some allies.
Joe and Braun Strowman are rumoured to be starting up a feud heading into Survivor Series so the seeds could easily have been planted here if WWE thought about the storyline rather than just about how they could surprise the WWE Universe.
Angle hasn't wrestled in WWE for more than a decade and even though he's been wrestling as part of other promotions, it isn't on the same level, so this idea could well backfire quite epically for WWE.