There are so many different ways this could go. I don't really know how I want Miz to come back. If Miz comes back as a heel then I'd want him to take over Del Rio's spot on Smackdown as the top heel over there and be the World Heavyweight Champion.
If he came back as a face I'd like him to feud with the corporation, specifically Orton.
WWE always messes up when it comes to Miz. Miz could be a top player in the WWE but they always miss-book him. I'll say my ideas for a return both as a face and a heel.
Face return:
If The Miz returned as a face, I'd like to see him return at Battleground. Just as it looks like Orton is about to win, Miz runs down and destroys him. Daniel Bryan ends up winning and faces HHH at Hell in a Cell for the WWE title while Miz faces Orton. Miz gets very close to winning the match but The Shield come out and attack him while Orton has the ref distracted. Orton hits the RKO and picks up the victory. Miz and Orton continue feuding to Survivor Series. I'm not completely sure what happens here. Either it'll be a singles match that Miz wins or It'll be a 5-on-5 Elimination match which Team Miz wins. If it's a 5 on 5, Team Miz will be The Miz, Dolph Ziggler, Cody Rhodes, Christian and ???. Team Orton would be Randy Orton, The Shield and Big Show as Show has officially gone heel now. The final 2 are Miz and Orton where Miz gets the clean win.
Miz would then go on and become a top face for the Smackdown brand.
Heel Return:
Again, Miz returns at Battleground. Everyone thinks he's come back to get revenge on Orton when all of a sudden, he attacks Daniel Bryan. He ends up raising Orton's hand as Orton looks confused. The next night on RAW Miz comes out and explains that the beating Orton gave Miz opened his eyes. Everyone ran to help Daniel Bryan when he needed it but when Miz was getting attacked, no one cared. He stood up to HHH when he should have been aligning with him. He blames Daniel Bryan for getting embarrassed in his home town. Daniel Bryan comes down and eventually a match gets booked between the 2 for Hell in a Cell. I don't really know who would win, but I think Miz should win with after HHH distracts Daniel Bryan. This leads to a 5-on-5 match between Team Bryan VS Team HHH. Team Bryan would be Daniel Bryan, Cody Rhodes, Dolph Ziggler, Christian and Big Show (he's a face for this scenario) and Team HHH would be HHH, The Miz and The Shield. Randy Orton is off defending his title against some other top face. Eventually, HHH gives Miz a World Heavyweight Title match so he can control more champions. Miz wins the title and goes on to keep it until either Wrestlemania or just after (depending on if WWE want to keep Miz's streak alive).
That's how I would book Miz's return, face or heel. However, WWE will likely bring him back and just have him feud with people like Fandango or Kofi Kingston and will keep burying him.