I'm adding this feature request to have high-rep users (15k?) to be able to migrate answers from one question to another, so that questions for duplicate answers can be consolidated.
Of course, there would have to be parameters, and a complete historical record, so that it could be reversed if mistakes were made. The questions would still be left pointing to the main duplicate (if there were multiple dupes, then there would have to be consolidation of that also).
Obviously, this would take some work to implement, since a complete interface to handle all the details would be needed, but I think in the long run it would add to the organization and usability of the site.