Prevent users from editing Core.Name property for existing nodes

Summary:

Lock on Commit, if enabled, prevents EDM users from editing the Core.Name property on a new node that goes through an approval process. How can we achieve a similar effect on existing nodes that may have been created before workflows were enabled (imported or mass uploaded before going live)? Making the Core.Name property not "editable" on viewpoint definitions locks it for even new nodes being created, so that is not the right approach. Please advise what other options are available. If we were to use custom validations, how can we distinguish between a "new creation" action versus an "update existing"