What happens when a user is reassigned to a certification is their latest unassigned Certification history record is restored. The user will also be placed back onto their their primary certification path.
I am not clear what you mean by clearing down all completion records - are you meaning deleting all historic certification records? If this is the case is there a problem creating a new certification and deleting the original certification?
Can you clarify what certification records from the old certification you want to keep?