2 headlamps on one band is a slick idea. I carry two headlamps, and my battery bank for my phone also has some surprisingly bright LEDs on it. I also always have 2, and sometimes 3 compasses. I am way more scared of getting lost or just not being able to find the boat I need to get back home than I am of needing a new carabiner or a second rope.
Black diamond on one side (white, red and green), 4 AAA rechargeable batteries one one side
Zebra light on the other (white), 1 18650 rechargeable battery on the other.
Just rotate the headband 180 and I am in business.