You could have it assign the lookupcomplete event when the onloadlookupfinished event is triggered instead of as soon as the form loads; I do that on a few of my forms where I run a few functions before I want the lookup events to be assigned/triggered.

$(document).ready(function(){
  // assign handler to detect onload lookup
  $(document).on("onloadlookupfinished", function () {
     // assign lookupcomplete handler after load lookup finishes
     $(document).on("lookupcomplete",function(event) {
       // your lookup event code here
     });
  });
});