EDIT: Addressing the bolded comment above - I just looked at a pic of the A-Basin hanger and it looks like he was on the downhill side. I'm amazed that he somehow got past the stop gate and past the bullwheel. No, I'm stunned. Where was the top lift operator? How did he miss the stop gate?
All the lifts where I work have that platform, after the bullwheel.
We were reading about this on the way home from Copper. Well, my wife was reading, I was driving. Because he was hanging from the chair, he apparently missed the stop gate by swinging outside of it. As we might imagine, it is designed for a
rider.
As far as banning backpacks, I don't think the backpack is the issue in and of itself. A typical daypack has nylon strap waist buckles. They don't support any weight like a hip belt, but rather just help hug the pack to your back. If you forget to buckle those straps, they just hang down loosely and definitely can settle between the chair seat and back rest. So when you try to dismount the buckle pieces can hang up in that space. I've done this myself and had to yank pretty good to pull them through. This can be difficult as the lift starts to pull you up as it goes around the bullwheel, but I dealt with it on a detachable (Pano @ Winter Park) so much slower and no quick drop away. Lenawee would not offer any material recovery time as compared to a typical detachable.
According to what we read, the lift operator did stop the lift as soon as he saw the incident, but as noted, it was already on the downhill side well past the platform. It also seems a stroke of bad luck or design to also then be hanging from the pack by your neck. You would have to come out of the shoulder straps entirely, but then presumably have had the chest strap buckled tight enough for your head to not slip through. So first rule on a little daypack is probably to leave the chest strap unbuckled. I never buckle that for skiing as I find it is restrictive and I'm never carrying any weight at a resort to need it. I don't know what else is on a pack that catches on a chair backrest. It's just a cushion. So leave the chest strap unbuckled - it is short, on the front, and shouldn't be able to catch on anything, and ensure the waist strap is buckled.
But the rescue is incredible - the pics are just unbelievable.