#4 Stardust
I personally would like Cody to return back as 'Stardust'. Before all of you burn me down (pun not intended), I will like to justify myself.
If Cody is given creative control, he can surely turn the 'Stardust' gimmick into something like 'The Demon King' gimmick of Finn Balor. We can see 'Cody Rhodes' wrestling on a regular basis and only calling upon his alter ego 'Stardust' when it is required.
With Cody himself showing interest in running the two gimmicks as two different wrestlers, WWE could certainly play a 'Corporate Kane/ Demon Kane' storyline here. Cody could certainly lead a demonic stable, like Ministry of Darkness 2.0 under his Stardust gimmick, having stars like Finn Balor, Bray Wyatt, and Aleister Black with him.