#1 The AEW roster is big enough for another Championship.
The simplest explanation for a new title in AEW is that the current roster is big enough to support another title. With the additions of Miro, Malaki Black, CM Punk, and Andrade, the roster is already stacked.
There are rumors that Daniel Bryan is heading to AEW so that he can also wrestle in New Japan. If that's true, he's another former WWE Champion that is worthy of a Championship.
Other big names like Adam Cole, Braun Strowman, and Bray Wyatt are technically free agents, but not for long. AEW is rapidly adding household names.
If one or all of the names other than Bryan join AEW, another title will become a necessity. There's so much talent in AEW already that the likes of Cage, Andrade, Pac and the Lucha Bros are yet to win titles. Andrade joined AEW only a few months ago and he's already been treated as a big deal.
Jungle Boy, Darby Allin, MJF, and Orange Cassidy are always strongly booked. With only a handful of titles to chase, it will be hard for these stars to win titles consistently.
Another title will balance out the immense number of talented stars. With more and more cuts from WWE, stars will be getting another chance at AEW. AEW has booked its Champions well for the most part, but not every decision will sit well with every fan.
For these reasons, adding another Championship to a growing roster would be a wise decision.