Scrawny -
You could probably fly a pre-rigged aircraft to a scene without issues and drop a harness on the end of a rope. (though this is against regs) The fundamental problem is you are relying on the subject to correctly get themselves in the harness. In my experience this is not going to happen for a variety of reasons. Unfortunately, a subject's emergency is our routine response and sometimes that response is not fast enough. I know that may sound callous, but virtually all of our subjects are in a situation of their own making. The day we start cutting corners and doing the headless chicken to speed up a response, is the day we will start killing ourselves, and that is not going to happen.