Ok, thanks. That helps. The answer you gave me just told me that you do not have ANY type of DNS or any type of trusts or ANYTHING setup. So...
Since this will be a DC all to itself you can go ahead and Create a new domain in a new forest. If you were to chose the other option then it would want to know the name of the DC that it would be a member of - you dont have that nor can you do it since the two sites dont see each other.
Then if you do decide to go with the VPN and they are then talking, you could dcpromo that down and make then chose the "add a domain controller to an existing domain" option later. There should be no problems with that. Then your DNS could be setup with AD-I (Active Directory Integrated) option.
We do migrations all the time and I work at an Enterprise sized company out of Nashville. We buy hospitals. We have over 120 hospitals and each of them had their own DC, etc.. that we had to dcpromo and all of that stuff. Some of them we had to set up site to site VPN's.
I know none of this is relevant to you or your scenario but I see no problems with you setting it up this way.
And no problem helping you on Saturday night. I am about to go to bed so I can get up for Church tomorrow. It is 10 minutes till midnight here and I am a bit tired.
I hope this helped you out and at least gave you some direction. It sounds to me like you already knew the answer - you just wanted someone else to justify!??! Dont second guess yourself. You sound smart.