The more I think on this, the more Awakner Ace becomes more interesting.
Ace is now, effectively a Fire Ghost. He came back because people love and remember him. Because people want him to live. He came back because he promised Luffy he won't die.
Sabo and Luffy. How will they deal with this? Good news, Ace is alive. Well. Not really. He's still dead. Sabo ate his fruit for sea's sake. He's a ghost hunting the world because he promised Luffy he won't leave him.
And his whole Awakner thing would make so many people terrified. Because his new body, no longer has Mera Fruit. It's entirely made up of Fire and Ash. An entirely different biology. Sea Stone no longer works. As long as his core is intact, he'll keep coming back.
Awakeners are also references to Lovecraft mythos, so an Awakener Ace most likely be tagged to something Other. Eldritch. Something would change him a bit more than only a body of fire that can't shifted by the sea.
Luffy would be more okay with it than Sabo, because Luffy accepts monsters into his crew all the time. (Luffy is a monster, with a touch of Other to him.) He'd still struggle, I think, tho, Ace is different now, even more different than Sabo who also came back.
Sabo...it'd be a struggle. He remembers the past because Ace died, he carries Ace's fruit, he's used to Ace being more human than Luffy, and he's a high ranked Revolutionary agent. As an agent, other is usually a sign of something about to go terribly wrong, not an adventure to overcome.










