I removed some silhouettes from the frosted plastic many years ago, using, I think, acetone. Left the frosted "glass" intact. (Worth an experiment on a small section. My memory may be spotty on this.) No making/cutting/fitting. Just put it back where it came from.
Actually, I usually have replaced the frosted glass (how often do you see this in real life...?), figures and all, with clear plastic. Even if the car has no interior detail, it can still look better than those foggy windows. I often disconnect the lighting, too - especially the older, big-bulb variety - as it is always daylight on my layout. My passenger business is minimal.