Hi again
I never tried pGina.
Documentation seam to say yes, if you correctly install pGina and maybe the krb plugin you should be able to do what you'r asking for. It's not Open Directory that support windows, it's an enhenced windows that is able to use OpenDirectory.
I suppose that you'll have to solve several crunchy problems and to modify the OD LDAP schema.
Schema modification won't be handled by WGM, so you'll have to find an other ldap editor.
Windows updates should make troubles too.
Regarding this, I suppose it should be more stable and straitforward to install SAMBA on your Mac Server.
After, maybe you like chalenges so have fun and try it 🙂
Bye
Nicoas