We should be thinking about replication from Windows to Netapp .
We cannot use snapmirror for replication between a netapp box and windows box. I think you have realized that one and we do not have native tools on netapp which would help in seemless replication.
Not replication but we can migrate the data using securecopy, F5 migration services or freetool available in windows which is robocopy. these tools will keep the security/NTFS ACLs intact during the migration.
Please let me know if this is not what you are looking for.