The individual cameras all need to be unlocked and need to be installed with adb.
You can’t install a private plug-in from the store or from another web site.
You can restrict use of your plug-in in the store by having the plug-in connect to your cloud-based site and requiring log-in from the plug-in.
Your staff or you can configure the plug-in with the credentials by using the web interface of the plug-in and storing the credentials on the camera.
A similar strategy would be to use a license or other key that is entered into the plug-in after installation through a web interface.
To install the plug-in on normal, non-developer-mode, cameras, the plug-in needs to be in the public store. There is no known workaround. Private companies are placing their proprietary plug-ins in the store and limiting access to their staff by requiring the plug-in to log into their site. Only their staff have the log-in credentials. The plug-ins are not used by the public even though the plug-in is in the store.