Alright, I was coming up with all of these complicated ways of doing this, and decided I should just add a filter to the theme to make it easy.
So in, GP 1.3.41, you’ll be able to do this:
add_filter( 'generate_navigation_location','tu_move_navigation' );
function tu_move_navigation( $location )
{
if ( is_front_page() )
return 'nav-float-right';
return $location;
}
If you don’t want to wait for 1.3.41, you can grab the latest files on GitHub: https://github.com/tomusborne/GeneratePress