Currently not with the cmdlets afaik, but with the API everything is 'posh'ible.
This will create a dummy VM and VMHost group, and then create a rule with both groups.
You can adapt the groups (for example add ESXi nodes) or change the type of rule
$clusterName = 'MyCluster'$cluster = Get-Cluster -Name $clusterName
$spec = New-Object VMware.Vim.ClusterConfigSpecEx
$newVMGroup = New-Object VMware.Vim.ClusterVmGroup
$newVMGroup.Name = 'DummyVM'
$newVMGroup.UserCreated = $True
$newVMGroup.VM = $null
$groupSpec = New-Object VMware.Vim.ClusterGroupSpec
$groupSpec.Operation = [VMware.Vim.ArrayUpdateOperation]::Add
$groupSpec.Info = $newVMGroup
$spec.GroupSpec += $groupSpec
$newVMHostGroup = New-Object VMware.Vim.ClusterHostGroup
$newVMHostGroup.Name = 'DummyVMHost'
$newVMHostGroup.UserCreated = $True
$newVMHostGroup.Host = $null
$groupSpec = New-Object VMware.Vim.ClusterGroupSpec
$groupSpec.Operation = [VMware.Vim.ArrayUpdateOperation]::Add
$groupSpec.Info = $newVMHostGroup
$spec.GroupSpec += $groupSpec
$newRule = New-Object VMware.Vim.ClusterVmHostRuleInfo
$newRule.Name = 'Dummy Rule'
$newRule.Mandatory = $true
$newRule.Enabled = $false
$newRule.UserCreated = $True
$newRule.VmGroupName = 'DummyVM'
$newRule.AffineHostGroupName = 'DummyVMHost'
$ruleSpec = New-Object VMware.Vim.ClusterRuleSpec
$ruleSpec.Info = $newRule
$spec.RulesSpec += $ruleSpec
$cluster.ExtensionData.ReconfigureComputeResource($spec, $true)