menu_item_weight_default.module

<?php
/**
 * @file
 * This module adds the ability do disable a nodes menu item from the node add/edit page
 */

/**
 * Implements hook_help().
 */
function menu_item_weight_default_help($path, $arg) {
  if ($path == 'admin/structure/menu/default-weight') {
    return '<p>' . t('Use this configuration form to set default weights for node menu items from the node add/edit form') . '</p>';
  }
}

/**
 * Implements hook_menu().
 */
function menu_item_weight_default_menu() {
  $items['admin/structure/menu/default-weight'] = array(
    'title' => 'Menu Item Weight Default',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('menu_item_weight_default_settings'),
    'file' => 'menu_item_weight_default.admin.inc',
    'access arguments' => array('administer site configuration'),
    'type' => MENU_LOCAL_TASK,
    'weight' => 6,
  );
  return $items;
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function menu_item_weight_default_form_node_form_alter(&$form, &$form_state, $form_id) {
  $node = $form_state['node'];
  $menu = $node->menu;
  if ($menu['mlid'] == 0) {
    // this is a new menu item
    $form['menu']['link']['weight']['#default_value'] = variable_get('menu_item_weight_default', 0);
  }
}