Ways to simplify conditional watermarks over images?

Hello, all!

I'm going to make some sample course content available on the web, and am exploring ways to watermark graphics and photos so that screenshots don't end up in others' projects. (I've seen courses from major agencies that include such content, created by people I know, without permission or attribution).

There will be hundreds of images to watermark in the slides' base and in layers, so I'm looking for a way to simplify the process. A file showing my initial attempt at this is attached.

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Details:

Currently, the watermark image (initial state = hidden) is over top of the graphic/photo, and it's only shown when the variable 'SAMPLE' (used when I publish for the web) = true.

Images that link to a layer have two triggers ('disable Next when clicked,' and 'show layer'). With the watermark over it, I need to copy these triggers from the image to the watermark for the layer to be accessible.

Other images use ‘Zoom Picture.’ With the watermark over it, the zoom feature is hidden.

I can't (I believe) use anything in a slide/feedback master, as the size and location of the watermarks need to be adjusted for many images. Regardless, with the watermark needing to be above the image, I'm not sure a master could be used.

With the attached file showing my starting point, does anyone have suggestions for how this task can be made less onerous? I'm fine with going in a completely different direction.

Note: The image placeholder at the left of the slide is a consistent 250 x 500 px, so I could create a watermark of that size and use hotspots over top--that'd at least reduce the number of them needed.

Thanks for your time. Any thoughts will be welcomed!