I wanna piggyback onto this comment to say that you can change the home launcher on a Chromecast With Google TV (And some other Android TV boxes) by downloading another launcher first (I use FLauncher) and disabling the default home launcher.
This will disable the service that re-enables the launcher
This will cause the home button on the remote to fall back to whatever other home app is installed. No button remapping needed. It will also break the YouTube button, but not the Netflix button.