[Raynor]

Originally Posted by Formendacil

Shall "Morgoth's Ring" be destroyed--the final end of Arda Marred?

There are two versions that I know of: healing - or recreation of Arda:

Originally Posted by Note iii to Of the severance, Later Quenta Silmarillion, HoME X

Since the Elves (and Men) were made for Arda, the satisfaction of their nature will require Arda (without the malice of the Marrer): therefore before the Ending the Marring will be wholly undone or healed (or absorbed into good, beauty, and joy).
...
But others use another analogy, saying that there will indeed be a New Arda, rebuilt from the beginning without Malice, and that the Elves will take part in this from the beginning.

Originally Posted by Athrabeth Finrod ah Andreth, HoME X

- [Those of the Old Hope] say, answered Andreth: they say that the One will himself enter into Arda, and heal Men and all the Marring from the beginning to the end.

Originally Posted by Lalwendë

"but don't worry, because whatever nasty stuff Morgoth has put into Arda, ultimately only serves to glorify me a bit more".

The more consistent answer is, rather, that all evil works for good, something you touched upon in your post. Tolkien had this idea about his created world

Originally Posted by Notes on motives in the Silmarillion, Myths Transformed HoME X

Manwe was the spirit of greatest wisdom and prudence in Arda. He is represented as having had the greatest knowledge of the Music, as a whole, possessed by any one finite mind; and he alone of all persons or minds in that time is represented as having the power of direct recourse to and communication with Eru. He must have grasped with great clarity what even we may perceive dimly: that it was the essential mode of the process of 'history' in Arda that evil should constantly arise, and that out of it new good should constantly come.

or real life:

Originally Posted by Letter #64

All we do know, and that to a large extent by direct experience, is that evil labours with vast power and perpetual success – in vain: preparing always only the soil for unexpected good to sprout in. So it is in general, and so it is in our own lives. ....