Yeah, I read this a couple of weeks back. The Red Skull segment was nicely done; Thanos is a Titan and the Skull is Tantalus. Condemned by the Gods(Stones)to see that which he desires most but never possess it
The Power Stone may return him to earth, now that he has served his sentence as Gate Keeper. Or, since we only saw one part of the planet, perhaps there is a civilisation on another part of Vormir that has the technology to send him home.
I don't think Red Skull will want to fuck with the Power Stone again, after what happened to him the last time. The Soul Stone is out, as to possess it, the person who seeks it must sacrifice someone they truly love. That's what made the Skull the perfect guardian; as a psychopath he is incapable of loving anyone enough to make such a sacrifice.
Realty or Time would be my pick.
When Red Skull meets Thanos and Gammora for the first time, he appears to be levitating. We don't know if this is a power he has developed during his long isolation or if it was granted to him by the Soul Stone. Will be interesting to see if he has any knew abilities next time her appears.