Con: Two Rumbles in one night can be overkill
This was a logistical challenge that was always going to be present. It's hard to escape the truth that holding two Royal Rumble matches on the same night could be a recipe for fan burnout, even if the two matches bookend the pay-per-view.
This possibility could have been mitigated had they chosen to do the Rumbles on two separate nights but that would present additional problems.
How it's structured will be crucial. Will there be 20 participants? 25? 30? What will the intervals be between entrants? All of this will affect the time elapsed. Given the female roster, a Rumble around a half an hour might be the ideal length.
The action inside the ring will be important too. For the success of the match, WWE should centre it around the more talented ring workers racking up quick eliminations of some of the less talented ones. Otherwise, it could drag very badly.