"So what brings you here -"

"Having figured out the oath reform - well, convinced Eru of it - they can reembody the Fëanorians now."

"I'm glad."

"I thought you'd like to know. I'm not sure if you want to be present..."

"Do you think it'd be helpful?"

"Maglor asked after you. - Maedhros preferred to be unconscious even once they had it set up so they could talk, I don't know what if anything would help him."

"'no people around' seems unlikely to be the trick, though. All right. I'll go - where -"

"The Lóriens are connected now; they'll start in this one and go into ours as soon as they can move around."

"I need a little time to keep things running smoothly in my absence."

Nod. "How long?"

"Depends how long I'll be gone, but say a day or two more here."

Nod. "I'll let them know."

"Thank you. And congratulations."

"Thank you."

And he arranges for a brief vacation.

And do any of the alts want to be there?

All of them do!

And she has been chatting with them enough that she will show up too.

Mandos reembodies them.

It takes a few days before even Fëanáro is steady on his feet and then demanding to be shown a computer and taught half-a-dozen languages. Maglor spends a month sitting alone, singing, though after a few days Lórien decides he should be next to Elrond doing this and he hugs him and talks with him over osanwë occasionally.

Maedhros does not move. Lórien does not arrange him visitors. The Valar keep him alive.

The ring informs Ambela that it could totally fix it.

No it can't, not really.

Can too really. 

If it cares to make a case based on premises other than "mind control is inherently great"...

It can do detail work. For, um, the purpose of torturing people until they're unrecoverable, admittedly, but you could also use it to do the exact opposite. Weaken all someone's associations to the last seven thousand years of memory, until they remember it like they read it in a book, amplify the flaws in all the hallucinations until it's obvious that the last escape was real and that the present world is genuine, find all the things that make him want to stop existing and make them cease to point his thoughts uncontrollably in that direction, make moment-to-moment existence nice or at least tolerable -