samba - May 2004 - idmap backend with Active Directory LDAP

Everything that I have read about 'idmap backend' describes it being
used
with a standalone LDAP server.  Is it possible though to configure Samba
to store idmaps directly in an Active Directory LDAP using 'idmap
backend'?

This would obviously involve some schema changes to Active Directory, but
other than that I can't think of any technical reasons why this would not
be possible.  I could be wrong is saying this though.

Thanks,
Ed