A guide with all traders would be great. There are several traders in game and sometimes its not clear who is an NPC you can barter with. Some of the merchants are out in the wild away from towns. I think you'd run into issues when listing what they sell. Since every trader has an inventory that resets daily and only have limited quantities.

I know early on I was hunting out every merchant I could find to buy items I had a hard time acquiring. Specifically straps and hide, pelt, fur. I ran into an issue where all wildlife stopped spawning for me.