Bear with me here. This may not look very elegant, but it'll get the job done. There doesn't seem to be any direct cmdlets for editing those values. Had to resort to other methods and properties on the objects.
You'll need your standard Connect-VIServer and Disconnect-VIServer cmdlets (just assumed you knew that already).
You may also need to change what's in the quotes in the $dvs line with the Get-VDSwitch command. In my example, my default switch name on my lab device was "dvSwitch"
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$dvs = (Get-VDSwitch -Name "dvSwitch").ExtensionData
$netShares = $dvs.NetworkResourcePool | Where {$_.Name -match "vMotion|NFS"} | Sort Name
$newSpec = New-Object Vmware.Vim.DVSNetworkResourcePoolConfigSpec[](2)
$i = 0
foreach ($shareItem in $netShares)
{
$newSpec[$i] = New-Object VMware.Vim.DVSNetworkResourcePoolConfigSpec
$newSpec[$i].Key = $netShares[$i].Key
$newSpec[$i].Name = $netShares[$i].Name
$newSpec[$i].Description = $netShares[$i].Description
$newSpec[$i].ConfigVersion = $netShares[$i].ConfigVersion
$newSpec[$i].AllocationInfo = $netShares[$i].AllocationInfo
if ($newSpec.Name -match "vMotion") { $newSpec[$i].AllocationInfo.Shares.Level = "low" }
else { $newSpec[$i].AllocationInfo.Shares.Level = "high" } #assume NFS since vMotion was checked before hand
$i++
}
$dvs.UpdateNetworkResourcePool($newSpec)
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What this does is essentially copy existing NetworkPool information into the ConfigSpec objects and then edits the $newSpec.AllocationInfo.Shares object (specifically, Level) to change from low to high (or normal if you wanted to set that). Specifically, this should get you to what you need (I hope!)
