#1 Aleister Black
Originally, it would seem that Aleister Black would fit better on RAW as Paul Heyman is supposedly a big fan of him. But on SmackDown, there is more potential in terms of story. Black's dark character should not appear on TV every week, so the shorter show could work well for him in that respect.
If booked well, his presence is usually a huge deal, much like in NXT. Additionally, his style of combat would fit right in with FOX's sports-centric vision for the show. The former NXT Champion is an incredible striker and can be pretty vicious in the ring.
Black has all the tools to become one of the biggest names on the roster and WWE would be smart to preserve his aura as much as possible. Also, the biggest feud he could possibly have currently would be on the Blue brand.
Bray Wyatt has been urging everybody to let him in, while Black has openly proclaimed that his door is wide open and he is waiting for a challenge. A feud between the two mystical Superstars could be perfect. The Dutch Destroyer is one of the only men who could possibly defeat the Fiend, so WWE must not drop the ball with it.
This is the biggest match either man could have at WrestleMania 36, only considering full-time performers, so WWE would be very smart to draft Aleister Black to the site of the Firefly Funhouse and build to the match very subtly.