I had the same problem a while ago. Our server had a hardware fault, and due to lack of equipment and difficulty getting repairs quickly here I had to setup a backup server. At one point I wasn't sure what the problem was, so didn't migrate the Zentyal module data over. That meant recreating a new domain.
I managed to get a semi automated structure set up, rsyncing all the profiles and data, script to add the users, another script to set the acls of ntuser.dat etc.
I actually worked very very well, at least for my userbase. The only thing lost was their passwords and their desktop images.
I started writing it up for work for future reference, but I'm not 100% sure I have all the info correct (it was a slightly stressful time).
If any of this sounds interesting to you, please let me know and I can send you further information.