Re: Certification costs would be enormous
I know that tandem parachutes -- at least when I was jumping regularly -- weren't certified by the FAA, which defined a parachute as a "dynamic deceleration device for a single individual". So, without the FAA certification, you had to fill out some rather extensive waivers in order to "buy a ticket to fly on one". Since more than 20,000 people were doing this every year, that wasn't too much of a barrier.
Cheers,
Nathan.