The application is roof inspection where you have a thermal image of the roof and a normal RGB image. The optimal/preferred way a roof tech or insurance company like to use digital imagery in that case is to scroll around the roof (this is like a 50,000 square ft warehouse roof, not a 3-bedroom home, mind you) and look for abnormalities in the thermal image possible indicating some type of defect or damage causing a cooling or heating leak. But then they want to immediately switch to the RGB view and zoom in to see what that section of the roof actually looks like in detail.
So a switch to toggle the layer off and on, or a transparency slider is needed to switch between them. Doing a 50% transparency image in a graphics editor and uploading it doesn't cut it.