It would be nice if the scars were to be mended, but it would not be right to do so, for obvious and not so obvious reasons.
If Illuvator were to mend the scars, he would be visibly and openly interfering in ME matters, which he doesn't do. After the Ring was destroyed, the Third Age ended, and the Fourth Age, the Age of Men, began. The First Age was the age of the glory and power of Elves, the Valar were still a part of ME at that time. The Second Age was the age of the glory and power of Men. The Valar were still a part of ME, but they didn't involve themselves in it's events until they were provoked, and even then they didn't do anything themselves, but laid their power before Illuvator. That pretty much ended the involvement of the Valar in ME affairs. The Third Age had nothing to do with the Valar. It was the age of the waning of Elves, and the waxing of the dominence of Men, for Illuvator, or even the Valar, to have done something that was visibly of their work in that age, anything at all other than attempting to influence events by means of things like weather, would have stopped the waning of the Elves for a long time, and interferred with the dominence of Men. Same with the Fourth Age, interferrence with events would have taken away the power of Men. The fate of ME was no longer in the hands of the Valar or Illuvator, it was in the hands of Men, to mend or mar.