Change content layout based on menu hierarchy

You can use wp_get_nav_menu_items to grab the menu in question,

then go through the array of items to output the content

function output_landing_page_content(){
    //grab the menu items in order
    $menu_items = wp_get_nav_menu_items( $your_menu_id, array( 'orderby' => 'menu_order' ) );

    foreach ( (array) $menu_items as $key => $menu_item ):

        //get post id of linked page/post
        $postid = url_to_postid( $menu_item->url );
        $your_menu_linked_post = get_post( $postid );

        //format content
        $your_content = apply_filters('the_content', $your_menu_linked_post->post_content);

        //display each page/post content however you want (add in titles, author meta or whatever)
        echo $your_content;
        echo '<hr />';

    endforeach;

}

just place your function in the template for your landing page