There isn’t a manual install option right now and the workaround we’ve recommended to others is to use a separate Google account they don’t care too much about giving more broad permissions to. We certainly aren’t using the permissions to access other sheets or data in your drive, it’s because of the way we “copy” solutions from our master template into customer sheets. There isn’t a way to do that without the use of the V4 API from Google and that’s what requires such broad permissions. Thanks for the feedback though.