I'm afraid that PowerCLI doesn't contain any cmdlets to create partitions.
But PowerShell does contain some cmdlets to create partitions, see for example A Woops–Creating Partition and Format disk using PowerShell does not update the $ share, a post from the Deployment Bunny.
But you will need to have an environment that has PowerShell and that can access the vDisk.
Should be easy, set up a VM and install an OS on there with PowerShell.
Then attach the new vDisk to this VM and do the partitioning and formatting.
Would that be a possible solution ?