If the polygons aren’t going to be visible and aren’t going to affect lighting then you can just delete them
What also helps is to reduce the amount of materials–so that object should be one material. For the buttons that light up you would use an emissive map. You can put a grayscale map into the alpha channel (if you don’t need an alpha channel) and then in your material you can multiply it against the RGB channel and then you’ll get a result that you can apply to emissive.
For parts that are just a single color that are among parts that need actual textures you can map some small color swatches in a corner somewhere and then just UV map those parts to the appropriate colors.