Is this the same shot, but with different color added to it in resolve? If so, resolve’s output will give you the same file name it did the first time. (if you output it to the same directory, i believe it will over right the original mxf) just tell resolve to use the source file name…assuming you did that the first time.
If it is a different shot, can we assume it has different timecode? If so, (its been a while but) even FCP would be unsure how to use this shot would it not? I would guess you would have to go in and adjust the shot anyway. Plus in FCP, would you not have to select each shot individually if they are named something different anyway?
Just thinking out loud here, but perhaps output a list from avid to Resolve. In resolve you can change the shots being used on the timeline using the conflict adjustment tool, or manually selecting shots and changing their source directory, or manually selecting shots and telling resolve to use a different shot from the media pool. Either way, you could swap the shots in resolve and output a new list for Avid to work with again. If it is pretty much every shot in the sequence, then you are looking at a lot of selecting and swapping out shots either way. Might as well just do a replace edit in Avid for each shot.
Glenn