A few sobering facts about explosives;
PanAm flight 103 was brought down by 250g or half a pound of Semtex.
HMX, the explosive of choice in the 21st Century is very much more powerful than Semtex.(the exact factor is in question but it is at least twice as powerful)
Octanitrocubane is a recently developed product which is again, many times more powerful than HMX. (thankfully it is very difficult to make)
From this it can be seen that even 100g of such an explosive, which would be more than enough to blow a large hole in a fuselage, can very easily be concealed in a bodily cavity. The example of a tampon sized sample of the explosive would weigh about 80-120g.
The human body would do almost nothing to dissipate or lessen the effect of either of the two latter explosives. The surrounding tissue, meaning most of the body, would vapourise under the intense pressure developed in the milliseconds following the blast.
The example of the Saudi assasination attempt is not valid as the explosive was certainly neither of those mentioned above.
Whether you agree with the use of the scanners as a crew member or not, you will find no assurance that the current scanning/pat-down system is able to detect a device as described. If a terrorist opts for the pat-down then it is almost impossible to see how such a device would be detected.
There should be no option for passengers, they should all be made to go through the body scanner. If that policy were to be implemented then it is hard to see how aircrew could justify a simple pat-down check. It has to be all or nothing.