Well most of the drops can be got from retainer ventures, and it would be welcome to get a boost for farming items :P
Maybe have like a sepcial rare item that you have to have killed 100 or something of a certain creature to get a drop rate of like 1%
for example, kill 500 of a Ixali Watchwolf and you'd get a 2% chance to get something like an unbreakable wolf fang, that can only be used in lv 50+ recipes?

And yeah an achievement by area, like the hunts. They could maybe be like ranked as well? So a lv1 nutmuncher marmot would be rank D, going up to rank A/S