Multi-Version jQuery on Crack

multi-version-jquery.js

function(my_selector) {
  var old_jQuery = jQuery;

  var doWork = function() {
    var my_jQuery = jQuery.noConflict();  
    jQuery = old_jQuery; 
    // load up myplugin on my_jQuery
    my_jQuery(my_selector).myplugin({...}); 
  }

  var head = document.getElementsByTagName('head')[0]
  var jq_script = document.createElement('script');
  jq_script.src = "http://ajax.googleapis.com/ajax/libs.jquery/1.4.2/jquery.min.js";
  jq_script.type = "text/javascript";
  head.appendChild(jq_script);

  jq_script.onreadystatechange = function() {
    if (this.readyState == 'complete' || this.readyState == 'loaded') {
      doWork();
    }
  };

  jq_script.onload = doWork;
}();

This is a braindump and untested. I maintain the datepicker plugin for trac. Often times, users have some ancient version of jquery that doesn't work with datepicker. This problem usually shows up on Debian, which provides an older version of jquery and strips the default version from the trac installation. I'm trying to brainstorm a safe solution to use a newer version of jquery for my plugin only. The constraint is that my code shouldn't interfere with the rest of the site. This solution could be slow, but at least it will always work(in theory). Perhaps I can wrap this code in a conditional driven by a trac configuration parameter like [datepicker] safe_mode = enabled.