WooCommerce Simple Custom product type w/ pre order suppor

/* STEP 1 */
function register_simple_custom_product_type() {

    class WC_Product_Simple_Custom_Product extends WC_Product_Simple {

        public function __construct( $product ) {

            $this->product_type = 'simple_custom';

            parent::__construct( $product );
        }
    }
}
add_action( 'init', 'register_simple_custom_product_type' );



/* STEP 2 */
function add_simple_custom_product( $types ){

    $types[ 'simple_custom' ] = __( 'Simple custom' );

    return $types;
}
add_filter( 'product_type_selector', 'add_simple_custom_product' );



/* STEP 3*/
function custom_product_tabs( $tabs) {

    $tabs['custom'] = array(
        'label'     => __( 'Custom', 'woocommerce' ),
        'target'    => 'custom_options',
        'class'     => array( 'show_if_simple_custom', 'show_if_variable_custom' ),
    );

    return $tabs;
}
add_filter( 'woocommerce_product_data_tabs', 'custom_product_tabs' );


function custom_product_data_panels(){
    global $post; ?>

    <div id="custom_options" class="panel woocommerce_options_panel wc-metaboxes-wrapper">
            <div class="options_group custom_simple">

                Hello

            </div> <!-- options group -->
        </div>
<?php

}
add_action( 'woocommerce_product_data_panels', 'custom_product_data_panels' );


function so_42253729_add_pre_order_support( $types ){
    $types[] = 'simple_custom';
    return $types;
}
add_filter( 'wc_pre_orders_supported_product_types', 'so_42253729_add_pre_order_support' );