#4. To promote another SmackDown feud into a Hell in a Cell match
If not Roman Reigns vs Rey Mysterio, there are two other matches from SmackDown that WWE could use the Hell in a Cell stipulation for. Seth Rollins vs Cesaro could be one of them.
New Champs in WWE! More RIGHT HERE
Another bout is the SmackDown Women's Championship match between Bianca Belair and Bayley. While this feud doesn't have much heat, it would make sense to give the two women a Hell in a Cell stipulation.
Last year, Bayley's historic SmackDown Women's title run ended at the hands of Sasha Banks inside Hell in a Cell. After headlining WrestleMania 37 Night 1, the history-making Bianca Belair successfully defended her title against Bayley at WrestleMania Backlash.
Since it's a title match, it would make more sense to give it the Hell in a Cell stipulation. Yet, many would argue that Seth Rollins vs Cesaro would be more suitable as they can use the steel structure better.
WWE has done three Hell in a Cell matches in one pay-per-view before, but that turned out to be more than what was needed. It was unfortunate that neither Women's title match got the Hell in a Cell stipulation, but that could still change.