public endpoint to resolve dynamic paths to node/id path.

I found that resolving the url with drupal_get_normal_path was helpfully to workaround having to use node/id

Perhaps you can add a oembedprovider plugin like...

$plugin = array(
  'title' => 'Node',
  'capture subpatterns' => TRUE,
  'scheme' => url('', array('absolute' => TRUE)) . '*',
  'callback' => 'oembedprovider_path_provider',
  'provider' => TRUE,
);

/**
 * The default provider to handle nodes
 *
 * @param string $url
 * @param array $matches
 */
function oembedprovider_path_provider($plugin, $url, $matches, $parameters) {
  $matches = explode('/', drupal_get_normal_path($matches[1]));

  ////////// COPY from node.inc  ....
  $block_endless_recursion = &drupal_static(__FUNCTION__, array());

  $result = FALSE;
  $nid = $matches[1];
....

Also it would be nice to have a oembedprovider plugin that accepts links without a url.. Like.

[embed]node/id[/embed] or
[embed]content/homepage[/embed]

This allows us developers to not worry so much when the base url needs to change.