i suggest an npc likeability where npc have 100 bar percentage points where you help npc from a certain quests that every help gives points that when you complete the 100 bar points it gives benefit like 5% discount on certain items.
or gift the npc for a certain category's item like leather, bullets,or miscellaneous items
And for non trader NPC when the players complete the 100 bar points its gives certain items every day like 1st aid,band aid, water or more like the npc in mcjoel farm who gives free alchohol bottle..
everyday when you complete his quests....
well this suggestion is beneficial and kill some boredom for us who completed the rest of the mission..
well this is just a suggestion feel free to change ,accept it or deny this...
IGN:lenz