It is a real need, but how-to gets messy. Long ago, a method was suggested but apparently is still a wish...
Select a database record in MC library, choose the wished-for option "Replace file, retain tags", manually locate and choose the new file, and MC would automatically copy all user tags into it, and then update the library to point to the new file.
Not a mass/batch process, because of the need to select each replacement file, but reduces the manual steps and does all the tag actions within MC.
A mass/batch process likely would involve something like giving all the new files the same names as the old files, then pointing to that folder, so MC knows what to do with what. Or perhaps naming new files the same as old files but with a special prefix or suffix, so they can be in the same folder as the old files. MC might process all the new files beginning with _NEW_, and leave behind all the old files renamed as _OLD_
Lots of ways to imagine this. But however it gets done, an MC built-in way to update files while preserving tags, with the fewest steps, would be a wonderful thing. Though, it's worth considering what can go wrong...
PS: I'm saying "files" rather than audio or rips or whatever, because this same file-update capability would be useful with video and image files too.
PPS: Seems like doing a true audio CD re-rip, existing MC library files replaced directly from the rip, would need to be user-steered, track-by-track, how else would MC know what to do? CD tracks are not named on the CD, so unless it is assumed that MC's database already has exactly the same entire CD, with correct track numbers, a hands-off process could be a train wreck.
This has been discussed at times over the years, as many of us realized our early rips no longer do justice to our sources, but also realizing it's a huge job to update them. It would be helpful if someone at JR could say whether doing anything along these lines would be considered, so we can either pile on or disperse...