Hmmm...one minor complication...I need a Windows Server flavored OS to create a domain. So I need to make a new machine? Or run one on a VM?
Yes and no. The Hyper-V host machine should never be a member of the domain it's hosting. This is because it should be a dedicated (to Hyper-V hosting) box (e.g. no AD), and therefore it can't login and authenticate to a domain controller that isn't running yet. So you either run the Hyper-V server(s) in a workgroup, or (if you need to use high-end stuff like Live Migration) in a separate domain.
I currently have 3 physical servers in the rack at the office. The two Hyper-V servers are in a completely separate domain from the production systems, and authenticate to a DC that runs as a VM on the third server which is basically an orphan. The production systems consist of 20 virtual servers for load balancing and redundancy and are spread across the two physical servers.
Having the DC start first is easy enough if the usual trifecta (AD, DNS, DHCP) is the only thing running on the VM, and the other systems are set to wait a minute or two before booting.
Your desire for ultra flexible drive usage may complicate this a bit as added/removed drives would need to sort out which system (physical/virtual/both) they were going to be accessible to.
Or run two DCs, one physical on cheapo hardware to allow the main host system (and guests) to boot cleanly, and one virtual to keep the domain intact in case the budget physical box decides to grenade some day down the road.
Warning: Virtualization is highly addictive!!