[Vultur]

I agree that the omission of any mention of Turin's return from Mandos (whether to slay Ancalagon at the War of Wrath or to slay Morgoth at the Dagor Dagorath) changes the feel of the story dramatically.

I'm not sure what other choice CT had, though, as Tolkien never settled on a final version of that bit. I think it was a matter of the original Turin story being incompatible with the universe of Arda as it developed, with Turin and Nienor becoming Valar, as the Doom of Men became a central element of the legendarium (as it wasn't in the Book of Lost Tales era, where 'Turin and Nienor become Valar and Turin kills Morgoth' came from) -- but Tolkien wasn't willing to discard the conception of his return in some form at least.

In a way, Tolkien thoroughly changed his views of the role of Men in relation to Elves in the final fate of Arda. In the early texts it's said that the fate of Men after the end of the world is not spoken of in the prophecies of Mandos "save of Turin only, and him it names among the Gods"; but later that is changed to it being said that Men will participate in the Second Music of the Ainur, and the fate of Elves is not spoken of. And then there is some discussion in Athrabeth Finrod ah Andreth about Men healing Arda in the end.

Essentially, the role Turin was meant to play (as representative of Men in the end of Arda's evils) became both irrelevant and impossible with later developments in the legendarium. So I'm not sure there was really any better solution than to leave the matter entirely out of Children of Hurin -- though it does seem crucial to his story.