Hi Styg,
I really like the game, including current trading system.
But I think some improvements can be made, without sacrificing its depth.
Here are some ideas.
1) Have "usually buys" description for each merchant, which would describe what kind of goods they would sometimes bye.
Currently, player only knows what merchant would buy at this moment, and not what all kind of items merchant could require later. By formalizing merchant roles this way, it will be easier for player to decide what kind of items to stash in vicinity for the future, when merchant requests get refreshed.
I think it would be easy to implement (merchant essentially already have those descriptors, they are just not exposed in the UI), and would greatly benefit the players, decreasing some tedium of the trading aspect of the game.
2) When in settlements, show player stashes as part of the inventory during trading.
Idea would be that when inside settlements, any stashes, that are owned by player, appear during trading.
This would streamline trading aspect of the game, without loss of depth and player would appreciate lower tedium during trading.
This would, of course, require implementing some kind of mechanic, that would mark specific container in the settlement as player stash, as well as what maps are part of the settlement.
3) And for the last, something more ambitious.
What if there is "global" trade screen for each settlement? Idea would be to list there all merchants that player discovered from the settlement, and buy things directly from there, without needed to manually go to each merchant. Only requirement would be for the player to be inside the settlement (no buying from Junkard, if in SGS).
Idea of this enhancement would be to additionally reduce tedium during buying/selling phase of player adventure.
I understand this one would be more tricky to implement, and personaly, I would rather get in-game map feature first, before this.