Here is another area that I don't think is paid much attention to, I'm not a medic/first responder, but I've been in a situation or two:

Dexterity/Ease of use - Things need to be easy to access or use, whether solo work on a victim or solo on yourself and it needs to be done with one hand. Possibly in gloves, whether latex/nitrile gloves or cold weather gear.

One handed, simple tourniquets like RATS are invaluable in this case (the windlass tourniquet you listed is good and effective, but I feel like it takes a lot more dexterity to work effectively with one hand), same with trying to open packaging for dressings/pills/anti-bacterials/liquids.

I'm sure there are lots of rules about how things like pills and liquids can be stored, but a little tear off packet sucks in a low mobility or challenging environment.

I put stuff like these in a plastic vial with a pop cap that I can flick off or force off with a squeeze or brush against something. Probably not realistic for a product, but something to think about.