I am looking for some assistance on how to enable guest customization for CIVM's at the VApp level. Currently I am using the $CIVM.ExtensionData.Section to enumerate guest customization settings and then using the .UpdateServerData() method to apply the settings. But this is run on each CIVM individually by cycling through the CIVapp. I have seen that there is a CustomizeAtNextPowerOn method in the extensiondata of the CIVApp but I am battling to figure out how to invoke this. I am looking for any assistance with this........
I had a similar issue and found this to be really helpful: http://wahlnetwork.com/2015/04/06/customization-specifications/
In order to change customization settings via PowerCLI for a template, you need to apply a Customization Specification when cloning from the template.
(I don't know if there is another method that doesn't require cloning ]: )
The guy explains his workflow of changing & applying settings, and even gives you a script that implements it.
Hope this help!