Well first there is a feature on some machines that you can pass through hardware in the BIOS. But I don't think that is still direct disk access I think that is some layer that you deal more with the hardware at SOME level and not go through layers of the hypervisor. Then you can create Raw Device Maps, which gives you Direct Disk Access, but managed by ESX.
Format is a function of the guess OS, not the host. VMFS is a file system on the host no the guest OS. So they are mutally exclusive. Windows can 'see' whatever disk you assign if it's a virtual disk or a RDM. Windows will have exclusive access to that portion of space you gave it, nothing else can touch it unless you explicit share it (or use Windows clustering).
So if you can use the pass through or RDM that can let you get access to the underlying hardware to configure / communicate directly to the disk, giving you physical access, but there will still be some layer of control by ESX, becuase that VM is managed by ESX.
I doubt you will every get 'true' direct access, just bypass some virtual layers. RDM is probalby what you are looking for, bottom line.
You set aside a LUN or some VMDK, give it exclusive access to Windows (or whatever guest OS you want) and that VM will have control over the space to format it as what is compatible. VMFS isn't really an issue, with 'direct access' or similar type functionality you wouldn't need to worry about the format.
