Anyone?

You're right -- there is no way to do it. As I understand the NTLM domain mechanics, there's theoretically no way to provide this facility.

It goes something like this:

When you join the machine to the domain, a machine account is created for the machine, and the machine gets the relevant encrypted magic that associates it with the machine account.

When you remove the machine from the domain, this magic is deleted.

Thus, there's no way of reconnecting the machine to the existing machine account without recreating the encrypted magic (which requires talking to the domain controller) -- hence the need for the administrator password.