How can I permanently disable (not uninstall) a stock app?
There is no way to disable an app for some users of a device but not others; it's possible to freeze an app using a third party program (ie, disable it by changing it's permissions so it can't run) but that will disable it for all users.  Android apps and services don't distinguish between physical users of a device - they all run using a single logical device user account.

That being said, depending on what exactly you're looking for it may be sufficient to disable data synchronization for a specific Google account in the settings.  In Android 4.4.0, this would be under Settings->General->Accounts->Google->[account name], which will bring up a checklist of services for which data syncing can be disabled.