I have never been sold on knife and headlamp as essential, if considering only an overnight trip. Proper trip planning can make the headlamp non-essential on short trips. I always think about setting up camp long before it gets dark. On most nights, except the overcast no-moon nights, your eyes will adjust to night time lighting. As for knife, all I ever use mine for is to cut food!
I assume the list is for what you would take on regular overnight trips in your area. We know we can survive with nearly nothing, but the list is mainly about priorities. If I were limited to 11 items, I would check the weather report and simply not go out if the weather were iffy.
1. Sleeping bag
2. sleeping pad
3. shelter - bivy sack- can sling over me if it rains
5. water bottle
6. insulating/wind proof extra layer with hood
7. 3 pound chunk of finger food- like fruitcake! Ha ha
9. first aid- if one item only allowed- large roll of FA tape
10. wool long johns (if cold) - or trade for camera if not cold
11. wool balaclava
I would not want to go more than overnight without sunscreen, toothpaste and tooth brush, lip balm, matches (fire building stuff),kerchief (my do-all item for towel, first aid, etc. Also would not go without mosquito repellant on if bug season. TP for longer trip. I think I would go without a bear canister even if required. I would just eat all my food at dinner and walk out the next day without food- no food to store, so still legal. The whole first aid thing is problematic if only one first aid item is allowed.