I understand Kovid's point of view about being paranoid about unexpected data loss. I was just making the point that if someone is designing/working on a replacement dialog or feature the reverse use case where newest wins is not that uncommon. The trick will be to come up with a user-friendly way of offering the user control without, as you say, an overwhelming number of choices.
If I saw a simple solution I would already be suggesting it
. Maybe a user preference with a simple way of toggling it might be the answer as one tends to be working in one mode during bulk import and another in daily library maintenance.