Never give up using Nethserver
I don't see the difference in setting up samba4 between Ubuntu server and the NSDC container with freshest samba 4.6.5, while actual Ubuntu has just 4.5.8. Maybe it's possible to use the smb.conf from Ubuntu directly in NSDC and "manually" join your Windows AD with "samba-tool". Or you could join your Nethserver to your Ubuntu server, so you may use the Ubuntu server instead of the NSDC container.
This one? https://wiki.samba.org/index.php/Joining_a_Samba_DC_to_an_Existing_Active_Directory
I tried it on NSDC with Win2003: https://community.nethserver.org/t/add-replace-existing-ad-domain-controller-with-ns7/4796/21?u=mrmarkuz
I personally think, what's possible with Ubuntu has to be possible with Nethserver too.
Yeah, me too, but finally we should get it there and I think it's possible!