You guys seemed obsessed with the idea that flight planning would have prevented the accident. I ask yet again, what do you think the pilot would have done if he'd planned over WLM and been refused a clearance by SY in exactly the way he was on the night? Answer me this: Why wouldn't he have pushed on in exactly the same manner?
Flight planning isn't going to stop this happening again as it will never guarantee an instant clearance or even a clearance at all. It will never guarantee the chosen route or preferred alternate routes are suitable for VFR. The pilot still has to decide "now what?". Pilot education will help and is more broadly applicable so will save far more lives.