Yes, it's pretty much like that.
The only issue you might come against is that WHS 2011 likes to backup the server to another partition. So you need another "datastore" or VM Disk in the same datastore to give you a partition that you can backup the server to (or use external disk via USB passthrough etc)
What I did
500GB drive (1 datastore - WHS 2001 OS and space for other OS drives in my ESXi environment)
1x 1TB Drive (1 large datastore - 1 large VHD - target for shared storage and client PC backups)
1x 1TB drive (1 large datastore -1 large VHD - target for server backups)
Spare slot. You can add a disk whenever, configure a datastore and VHD's and add them to WHS as new drives. They initialise using Windows Disk management and away ya go
Crucially, I installed ESXi to a 8GB USB stick which means that all the disk storage gets used for VM's rather than the hypervisor. Works very well on the Microserver (Done this on an older one and on the latest N40L equally successfully)