For some WILD speculation that I don't think would likely be the case but is fun all the same...
First guess is, now that (hopefully) all the zombies are rigged with the new decapitation system, you've made zombie heads an item you can pick up off the ground and you have to bring say 10 zombie heads to the trader
And for the second one, I'll guess something like Secure Trader so when you complete a mission tier you have to go to the new trader location, clear out zombies and then retrieve a bunch of supplies to fix the place up before that trader becomes available to you