I'm not sure what problem you would have doing that. The setting is an instance, not database level setting...when you restore the database backup that came from a "mixed mode" server to an NT-only server, the native users will create but they'll probably be orphaned users, showing up as "SQL user without login" in the GUI.
I guess you could drop those users and map out new NT based login/users to your database as part of a script. But there is no (that I'm aware of) database level setting for authentication mode, that is chiefly an instance setting and enforces against connections at a login level.