Migrating from an existing AD to a non-existant OD

So I’ve read through the AD/OD “Magic Triangle” guide and it doesn’t quite describe what it is we’re trying to do.

Currently we have a Win2K Active Directory with about 20-25 clients, 4 servers, and about 30 or so users. We are not utilizing network homes. We also have about 40-50 OSX 10.3/10.4 clients without any directory-based authentication. Just individual users setup on individual machines, and un-bound servers maintaining their own user lists.

We have an XServe running 10.4 (with no intentions to jump to 10.5 right away).

What we would like to do is make the XServe be the primary domain controller so that the existing Active Directory is nicely meshed with an as-yet non-existent Open Directory. We do want to maintain the ability to apply Group Policy objects to the AD, but we also want to make sure we only have to setup and manage user accounts in one place – preferably the XServe. We’d like the OSX clients to bind to the OD, and the Windows clients to bind to the AD, but is it really necessary to have the AD servers bind to OD and vice versa? In otherwords, do we really need the complexity of the “Magic Triangle”?

What’s the right way to go about this? I’d like to avoid having to move all the AD clients to a new domain if possible since they’ll be the most impacted by the switch.