To me, this is more of a function of experience. We can show people what to do and when, but they'll still be like a deer in the headlight when presented with similar yet somewhat different scenarios. I think it's a noble aspiration, but I don't have a clue how to raise their panic threshold, especially since we aren't allowed to do harassment drills anymore. I feel that they were not only great for the new diver, but they were fun as hell for everyone.
Slight hijack...
I recently took OW cert. Was very disappointed at everything being so super structured that you never had to do anything you hadn't had tons of time to think about first. Example: OK, show me you can CESA now...I take two nice full breaths...at the top of the 2nd one start swimming. HA, like I'll ever CESA under those conditions. I have never been super comfortable in the water and was looking forward to SOMEthing harassment-like. Alas...
Maybe I've watched too many Navy Diver/SEAL/PJ training videos, but that sort stuff (probably not so extreme though) looks very useful to me if I'm going to be safe in the water in any sort of surprise situation.
/hijack