#4 Ambrose's idea of returning as a heel was shot down
Dean Ambrose missed last year's WrestleMania due to an injury. He wanted to come back as a heel and have his character go in a completely new direction. Ambrose met Vince in New York and pitched a feud with Seth Rollins, or a move to SmackDown Live. Unfortunately, WWE had already advertised The Shield for Australia's Super ShowDown event in October, which meant that he couldn't turn heel any time soon. Ambrose wasn't too thrilled with it.
Also read: First photos of Super ShowDown stage construction revealed
Long-term planning seldom works. Remember how WWE began planning a Women's Title match between Ronda Rousey and Charlotte at WrestleMania 35, around a year in advance? Becky Lynch's popularity forced the company to change plans in a hurry, and she ended up winning the match she wasn't even meant to be a part of.
Similarly, advertising The Shield for an event several months down the line wasn't a good idea, as it put a brake on potential plans and angles that could have been done in mid-2018.