So a few things. As of the date you asked this, yes it was not possible to pick any template other than the standard one for a Home Page. However it was possible to create an App Builder Lightning App tab with a one-column layout, or a Lightning Component tab. If you remove the Home tab completely from an app, name your custom tab Home, and place it as the first tab, it will effectively act as the Home tab.
However there is now one more option as of Winter '18: Custom Lightning Templates. You can create a very bare-bones template component that implements
lightning:homeTemplate and has only one region. Then you can use that as the App Builder template for your Home tab and drag your component into it.