Is there a simple way to alter core node/add/my_node_type to adding/my_node_type?
I didn't test this code, but if I'm not mistaken, it should be as simple as doing this in a custom module:

function YOUR_MODULE_NAME_menu_alter(&amp;$items) {
  $items['adding/my-node-type'] = $items['node/add/my-node-type'];
  unset($items['node/add/my-node-type']);
}


Something similar could be done for the editing path.