You can access the webapi from within the plug-in, either directly or using something like theta4j.
This article is old, but it may still work.
In the current plug-in architecture with the Z1, you cannot access the USB port from the plug-in. You would need to use the camera itself to transfer the images to your cloud or you can stop the plug-in and then use the USB interface to transfer it to a small computer.
I believe that you can start and stop the plug-in from the USB API, but I have not tried.