One thing I'd really love to see is an NPC in every playable city/settlement (Allanak/Luir's/Red Storm/Morins) that just buys every raw material (shell/hide/bone/stone/meat/herbs/etc) really cheaply. Like 1-2 sid per item cheaply, without limit on the items. To prevent abuse, it could be capped at something like 30 sid per character per IC day. It'd allow characters to sell off things they accumulate for a pittance. It'd be way more profitable to sell things to the shops like normal, or to other PCs, but it would smooth off some rough edges on immersion when it comes to hunters/grebbers leaving things behind because they know they'd be unable to sell them even if they really should be able to pass them off cheaply.
The items sold to this NPC could be available to buy at normal prices for a short time - maybe an IC day or two? I think this would encourage the people that need materials to end up going there to check for things, running across the people selling them, and cutting out the middleman.

Make it like the buyer in the Blackwing Outpost. Y'all know which one I'm talking about.
My obligatory yearly rant on this subject:
Have ALL NPC buyers be able to buy a small number of EACH item from EACH PC, per day/week/month of real time. You can reduce the value of the items in question with each subsequent sale during that window of time. For instance:
Amos has 4 red widgets, 7 blue widgets, and 2 orange widgets.
Kadius will buy up to 2 of each item from Amos. So he can sell 2 red, 2 blue, and 2 orange widgets. The consequence to Amos:
He can sell one of each, with the haggle skill at max, at 50 sids each. So he would net 150 sids from the first of each color he sells.
The second (and final) one of each, the most he can make with max haggle, will be 25 sids. So that'd be 75 max for the second of each color combined. And a total for the RL week of 225 sids.
That might not sound like a lot, but he can ALSO sell 1 of the red and one of the blue at the generic tradesman for an additional 100 sids. And because widgets are containers, he can ALSO sell one blue one to the container guy down the street, for 400 sids. This means he'll still have 3 blue widgets unsold, which he could try and sell to actual PCs, or give as a "donation" to the local law enforcement, or gift to their mate, or whatever else.
That means he just earned 400 sids for just one item in three different colors. He could make serious bank if he was serious enough to make thingamabobs and sell those as well.
But he'd have to put in some actual work, he still has a limit to what he can SELL to an NPC, but the player eliminates the frustration of going to all the shops only to discover that Randy the Stump beat him to the 5 max per BUYER, rather than the max per SELLER.