#1 The Undertaker
This might seem like a ridiculous idea, but let's be honest, at this point in his career, The Undertaker is a severely limited performer in the ring, so why not take him out of the ring where he can use smoke and mirrors?
Having The Undertaker just walk around backstage with the title wouldn't fit his character, so instead, WWE could find a creepy property in the middle of nowhere, label it as "The Deadman's" home, and have various stars attempt to invade and take the 24/7 Championship from him.
All of the segments could end up being better versions of what they did when Randy Orton fought Bray Wyatt at the "Eater of Worlds'" compound. If that idea works, then it would really help get the title over, and it'd take whoever ended up defeating The Undertaker to the next level, and perhaps turn them into a main event level star on WWE's roster.