While your question is valid, I think it is symptomatic of a more general deficiency in MC: the need for a more robust way of handling re-ripping or otherwise replacing files in the library. The challenge is not just that you need to replace the file (you could theoretically do this in windows by using a utility like RoboCopy to copy the new files over the old ones), but that you also need a way of moving the tags from the original files to the new ones. "Copy Tags" only works for one tag at a time; "Rename File" in MC is too smart for its own good in this instance. I even tried "search and replace", replacing the old directory with the new directory, in hopes that I could replace the old filenames with the new and then use "write tags (from library)" to store the tags in the new files. But MC was too smart. When I did a search and replace on the filename, it moved and renamed the files! Granted, most of the time that would be exactly what I would want, just not this specific instance.
So, I take this opportunity to repeat my request for a "replace existing files" mode of some sort, so that those who decide to re-rip or for some other reason replace files in their library can do it with the same ease that MC enables them to do everything else.
OOH! I just thought of another feature request: when ripping, have MC determine if a duplicate song already exists in the library and warn you with an offer to not rip the file again, replace the file with the new one, or rip a second copy of the file. This situation comes up when, e.g. I'm ripping a "best of the 80's" album, and there's a song on there that I already have because I own the album it came off of.