This would almost work. However, if the original traveler's boarding pass happened to have an SSSS on it, then first of all, you wouldn't be able to obtain that boarding pass from a machine. You'd have to get the original traveler to come to the airport with you to present his ID to the airline ticket counter. Since the original ticket holder has driven all the way in to the airport with you, he might as well stand with you in the security line, get SSSS harassed and let the TSA initial or punch-hole his boarding card.

Now, at that point, you can send the original traveler home and keep his punched or initialed boarding card.

If there were some way to get an SSSS boarding card from a machine or home computer, you'd still have to figure out how to duplicate TSA's mark to make it look like the original traveler had been harassed. Making the TSA's mark varies from ridiculously easy to difficult in different airports.