But, like...Dealers could and 100% would still be able to craft more ammo in the field. If your Scout runs out of Bone Arrows congratulations the Artisan in your group can craft more on the spot still. But wait, what if your Artisan doesn't have the materials to craft you more ammo for some reason? Oh right. This suggestion takes effect and you can use crappy, already free base ammo instead until everyone's ready to finish their grind session instead of having to stop and go back for materials or more ammo. This isn't a suggestion for changing Ammo materials to something easier to find or things more commonly dropped. That's a good idea, make a new post for it if you feel this passionately about ammo crafting.
Also, people who never go back to town for more food, ammo, etc and live off of their loot can still do that. It literally wouldn't change their preferred, niche playstyle unless they wanted it to change it. They can still play how they want to.