Is there a way to skip bootstrapping drupal to save load time via drush?
That is hard-coded for each command: The module defining a Drush command sets the bootstrap level required to run the command. For example, cache_drush_command() defines cache-clear as the following:

  $items['cache-clear'] = array(
    'bootstrap' =&gt; DRUSH_BOOTSTRAP_MAX, 
    'description' =&gt; 'Clear a specific cache, or all drupal caches.', 
    'arguments' =&gt; array(
      'type' =&gt; 'The particular cache to clear. Omit this argument to choose from available caches.',
    ), 
    'callback' =&gt; 'drush_cache_command_clear', 
    'aliases' =&gt; array('cc'),
  );


To require not bootstrap at all, the "bootstrap" property should be defined as follows.

  $items['xkcd-fetch'] = array(
    'description' =&gt; "Retrieve and display xkcd cartoons.", 
    'arguments' =&gt; array(
      'search' =&gt; 'Optional argument to retrive the cartoons matching an index number, keyword search or "random". If omitted the latest cartoon will be retrieved.',
    ), 
    'options' =&gt; array(
      'image-viewer' =&gt; 'Command to use to view images (e.g. xv, firefox). Defaults to "display" (from ImageMagick).', 
      'google-custom-search-api-key' =&gt; 'Google Custom Search API Key, available from https://code.google.com/apis/console/. Default key limited to 100 queries/day globally.',
    ), 
    'examples' =&gt; array(
      'drush xkcd' =&gt; 'Retrieve and display the latest cartoon.', 
      'drush xkcd sandwich' =&gt; 'Retrieve and display cartoons about sandwiches.', 
      'drush xkcd 123 --image-viewer=eog' =&gt; 'Retrieve and display cartoon #123 in eog.', 
      'drush xkcd random --image-viewer=firefox' =&gt; 'Retrieve and display a random cartoon in Firefox.',
    ), 
    'aliases' =&gt; array('xkcd'), 
    'bootstrap' =&gt; DRUSH_BOOTSTRAP_DRUSH, // No bootstrap at all.
  );


Using DRUSH_BOOTSTRAP_DRUSH says to Drush that Drupal doesn't need to be bootstrapped at all.

Clearly, that is not something that can be arbitrarily changed; it depends from the code executed from the command.