Using just sunrise.php and the domain_mapping table, with the domain-mapping plugin removed from the mu-plugins, setting the wpurl and siteurl to the mapped domain makes everything work, without having to go through the trouble of the redirects.
Which leads me to believe that a domain mapping plugin that sets the wpurl and siteurl in that blog.id's options would be sufficient.
Which means a plugin like this written that allows you to add/remove from the domain_mapper or 'reset' from the wp_blogs would be more valuable and less intensive with the SQL calls per user.
When primary domain or reset to original wp_blogs domain is triggered it updates the wpurl and siteurl in the options.