When I've done these types of deployments, I've used the install key to install Windows, and not worrying that Sysprep will remove that key. Then use another XML for the sysprep /unattend which has the activation key in it. Of course you are using a deployment solution I have no experience in, so hard to translate that. Sorry, I confused installing the product key with activation. You are right the product key remains installed but the client still needs to activate with a KMS host once the machine is built. Our product key requires MAK activation so rather than configuring a KMS host, I've included the product key in the Unattend.xml file and under the <FirstLogonCommands> I'm running a slmgr /ato to activate windows.