This would certainly be interesting if it did happen within the next few years! It also wouldn’t surprise me if it did happen; Nemesis has actually had sections of track (or at very least supports) in the helix replaced before due to stress, and the vertical loop seems to have become quite problematic in recent years from a structural point of view.
From a ride experience point of view, also, I’d personally say the ride is certainly beginning to show signs of age now. While I wouldn’t call Nemesis a rough coaster per se, one or two of the inversions are getting a little bit jolty now; the second corkscrew and zero-g roll seem to be the key offenders for this, and I often come off the ride with somewhat sore ears nowadays when I perhaps didn’t a few years ago. If they could smooth out these inversions, I think my love for it would go up to an extent. Although with that being said, I’m not actually sure how much a retrack would affect the ride from a smoothness perspective unless they made profiling tweaks of some form, as based on my experiences with Hulk at Universal just 3 weeks after reopening, it didn’t seem to do an awful lot for that ride.
It would certainly be radical to see Nemesis get overhauled in this way, but I don’t think it’s out of the question; Merlin have seemingly allowed for Shaman at Gardaland to get fully retracked in this manner, and they practically fully retracked Colossos at Heide Park, as well, so I could definitely see them potentially allowing one for Nemesis in the not too distant future, especially if they could get some form of complete brand refresh out of it in the same way they did for Colossos at Heide.
