Hello,
Since now all the 11.x clients are now reporting to SEPM 12.1, you can simply create a custom Package without Network Threat Protection and Assign to each group for these clients to AutoUpgrade.
NOTE: Upon Installation of the Latest Package without NTP, the machine would require a restart to uninstall the Previous NTP.
Upgrade client software
NOTE: Clients that are Group Update Providers must be upgraded first (Group Update Providers are not a feature of Small Business Edition).
Review applicable steps in Steps to prepare computers to install Symantec Endpoint Protection 12.1 client, and choose from available methods to upgrade clients to Endpoint Protection 12.1:
• AutoUpgrade*--assign client packages to groups in the Manager console, either manually or by using the Upgrade Groups Wizard.
• Permit product updates in LiveUpdate Settings policy for a client group in the Manager console.*
• Local installation from product disc.
• Run the Client Deployment Wizard from the Manager console. It will walk you through the creation of a client package that can be deployed via a weblink and email, remote push, or saved for later local installation or deployment using third-party tools.
* Methods marked with an asterisk are not available in Small Business Edition.
Hope that helps!!