User blog comment:Wrath022/Chapter 516: The Truth About Enchantment, Review/@comment-7418318-20170101085701

Now Irene has a body that has both enchantment magic and healing magic.

Sounds like the perfect combination to fix her original body if she could be convinced to go back to it.

Also with Wendy's magic and Irene's experience I wouldn't be too surprised if it was possible to not only repair the damage that Erza did, but also turn the body into an actual Human... or at the very least give it Human sensations back.

Just because Zeref couldn't do it, doesn't mean it's impossible. After all it doesn't seem that Zeref can use healing magic, so this might very well be the missing piece that allows the full restoration that Zeref couldn't do.

This might also have an impact on the upcoming movie if you think about it. If the movie plays out after the current point in the manga and Irene is nakamafied, she and Wendy could cooperate to undo Natsu's dragonification we saw on the movie's teaser-poster.