First of all, I disagree: you need fewer people for the sniffer than for the X-ray, because the sniffer is automatic.
Second, I don't want to scare you, but what happens if I'm a suicide bomber and I go through this machine and blow myself up? Do you buy a new machine and a new terminal? What do you do?
You can only detect a suicide bomber when he's at the machine, because you don't do anything before or after it. That's my point. If I really want to inflict harm on an airport and I'm a suicide bomber and you don't have any means of profiling me before I get there, I could get five of those guys in front of five of your scanners and the whole system is gone.