Stitching yourself up is a quick way to get sick. The progression of sickness is still pretty quick too. You've got about 20 minutes before you wont be able to see anything and your hydration becomes an issue. That said, you almost have to try to get it, make a pretty silly mistake, or have some terrible luck. Have drank through it recently.
Cold status is definitely there, but you almost have to try to get it. TTSKO's heat value is super high, mix that with a little long distance running and you'll find yourself rolling around in water to keep from going into overheating. Hang around an area too long without drying off, and you'll get frosty. Still, a light jog will get you back into hot status.
I'm hoping the end-game to the weapon type and ammo spam is based off of percentages. In a harsh over-simplification of the loot economy, if they make military grade weapons 1% of the total weapon loot table, and civilian weapons 4% of the total weapon loot table, then the more weapons and ammo you add to the game, the less chances you'll find the proper weapon and ammo. If this implementation of accessories on pickup weapons goes through well, I'd suspect the chance for default ammunition as well. Thus scarcity. (%'s not to be taken literally)
I think the more generous they are with threats like wolves and zombies, the more generous they can be with the matching ammo and weapon ratio, while prevent that walking arsenal culture.