Unfortunately, replacing x-rays and metal detectors would probably make the screening process quite a bit longer, necessatating even more screeners. You would also need somebody available that speaks one of the several dozen languages and dialects commonly heard in some airports. And there is nothing preventing the determined terrorist from training on how to not trigger suspicion.
People need to realize that the current checkpoint security procedures are just one layer of the overall security system. Metal detectors, X-ray machines, behavioral observation, FBI watch lists, Air Marshals, FFDOs, aircrew procedures, employee background checks and even passenger attitude are just some parts of the system. None of them is perfect by it self, but putting them all together creates an effective system. Like stacking up slices of Swiss cheese. You can look through the holes of each slice, but when they are stacked up, they become opaque.
I think adding the behavioral questioning like the Israelis sure couldn't hurt, but are we willing to play the fiscal and temporal price. To continue the rant; Requiring uniformed aircrew to do the whole X-ray/metal detector when they are going to be at the controls of an aircraft in an hour is very illogical. CREWPASS needs to be up and running full speed yesterday!