Ability to either merge fields or change field(s) linked to an activity Merged

I spoke to a customer recently who works for a large potato producing company, and recently did a MyJD import. Needless to say her data was a big mess - she accidently imported new fields instead of matching existing ones. In order to fix this she has to go into each activity, delete it, and then re-enter it to the correct field, followed afterwards by hiding that invalid duplicate field. It would be an enormous time saver if we could allow users to either merge fields together, or allow a user to edit an activity and change the field (without having to delete the whole activity).