Google is already doing this with their default Android TV launcher. I tolerated their home screen 'recommendations' for a while as they occasionally highlighted something interesting to watch, but one day I switched on the TV and was greeted with a huge advert banner for a fucking watch on the home screen.
At that point I spent a few hours setting up FLauncher on all my ATV devices.
I can't speak from experience as I don't own any Amazon devices, but I have read reports that it seems to work fine with the FireTV variant of Android.
The dev has only tested it against Chromecast with Google TV, with that said I'm using it on a Shield TV and a Shield Pro and it runs fine on both.