Not that it affects your point, but that reminds me that the way the story was originally told, Michael's family name had been Garrison when he worked for the Loves, but he later changed his name to Hudson (making it hard for Marley to track him down). If he had too many links to an existing family, you might have to explain why Donna never had the opportunity to confront him in Bay City earlier. But I suppose it wouldn't be any harder than to explain how Michael found the time between leaving Donna and losing John in Vietnam to force his mother and brother to adopt the name Hudson as well.
If they had kept the Garrison name for Michael, I assume Grant and Ryan would never have been called Harrison.