I hadn't thought of it this way (I do it naturally), but designing a kit around not needing the next level is a great way to do it. For example, a device to help remove a foreign body blocking an airway BEFORE a surgical airway is needed. Or a chest seal before you have to needle decompress in the field. You always want to have the ability to address problems while they're as small as possible. Only preparing for the most life threatening injuries could miss that and reduce your odds of survival in some cases. Like not dealing with a small lac. That could eventually require IV supplies, surgery, abx, or even higher levels of care that you may not have access to right away.