There is no benefit to upgrading to a more recent service pack before upgrading to EV8. I also recommend SP4 since it has all the hotfix rollups from SP3 plus the move archive utility.
Concerning the restoring to Exchange... ??? Why? After you ...
Another option, if you allow user's to delete from their vault, would be to use the Virtual Vault. She could move items into different folders, delete items, delete folders, etc...