I think you should still consider those budget version rear view camera package with screen embedded into the rear view mirror. I originally thought the rear camera screen would be too small to see. But after I saw one on a Lexus CT 200h, I changed my mind as the image was very sharp and clear. It's very useful during the backing up. The OEM one with bigger 7" screen should be much better but you have to buy a 7" screen or a audio head unit with a screen which will cost more.I plan to install one on my 2016 base model (can't believe it's not standard on all). I never thought of installing it anywhere besides OEM. What are the benefits?
The local car audio shop doesn't have a kit for the current model year but offered a replacement rear view mirror with a camera embedded. Not sure if I like that idea (vs using the 7.1" screen). What brand are you looking at? Will you install yourself?