Also, as other people have suggested... it would be nice to be able to trade for uncut gems, and/or use cut gems for more things. Bags with sand in them?
It would also be nice if the counteroffers would not include things currently banned for export. Very annoying to fail a trade because the traders want the banned things and won't accept other items instead...
And will the stupid humans stop bringing me 6 iron anvils every year? And gear I can't use.
If no trade agreement is made or no specific items requested, I would like to see more varied and random selection of items carried. Typically they bring way too much cloth and leather.
Also, I would like to see the traders drive a harder bargain, or an significant increase in their prices. It is very easy to buy out every caravan that comes by making only rock crafts.
This becomes even easier once the goblins start attacking, because their gear can be sold for incredible value. Now, sure in 33a this is not an problem since the goblins are bugged, but once their behavior is fixed, I think something should be done to reduce the value of their gear.
What I tend to do is just buy everything that I can make use of at some point the first time or 2 that they show up. Then you have a high enough trade count with them to merit an agreement. Now you buy just the stuff you want them to bring all the time. You negotiate for the same stuff at the max price for the next year. The next year they will show up with a bunch of that stuff and a little bit else. Just buy all of the stuff you want them to bring and nothing else. Negotiate a small price increase for that stuff. The year after that they are fullly trained, and you can get that group of items at regular price in large quantities.