EDIT

We need a final implementation with a new wizard including the question if the name in sources should be taken from the accepted taxon if being empty and removing the second label.

From Ticket #3472:
What about checking all elements to move (including the description itself?) if they have sources with empty name in source. If yes have a dialog and ask if the empty name in sources should be set to old accepted taxon automatically and allow yes, no, cancel. Only then open the ordinary dialog/assistant.
Maybe only check sources of type primaryXXX, no import sources.

also have #3472#note-24 in mind