A new option for the newspaper
As we have the newspaper in the game, why don't we use it not only for advertising the things we sell but also for posting orders for the items we'd like to buy? You could add to the newspaper another page with user's orders, and those we could fulfil in the same way as we load the train. Each player could be allowed to post one free order for a certain period, just like the free promotion in the shop, maybe additional orders for gems, like additional promotions, too. Of cause, the items ordered should be prepaid by the buyer, and the seller shold get the money as soon as he submits the goods.
Sign to Advertise our Farms
I would like to suggest adding a sign of some sort that players could take advantage of (or not) to "advertise" what they're selling. For example, when a player visits another farm, there could be a pop-up that announces to visitors whatever message that farm wants to say, like "Welcome to XYZ Farm". Alternately, it might also be used to advertise what the farm might be specializing in (if anything), such as "Chocoholica Farm - Chocolate Goods Galore" or something like that.
If a pop-up might be too distracting, then perhaps it could be a decoration that a visitor could tap on that would expand to show the message.
Such a sign or decoration might be helpful, as it might guide some players to start to specialize in what they sell, especially now with more livestock feed being needed and taking longer and longer, and some players might not have the crops needed to craft feed but would gladly buy it from someone else who is specializing in it.
Not sure how viable this idea might be, but just thought I'd put it out there.
Specialty License for market items
Charge us 10 gems to sign up for a speciality license in the market, where we can only sell a certain category, for example, crop items, crafting items, baking items, sushi items etc. Then the people who sign up for this will be signed up for a speciality newspaper each of the categories. Then when trying to fill train orders or order warehouse orders, creating items etc, we will be directed to people who will be selling items in that category. It doesn't guarantee we'll get the exact item we want, but it will give us a chance to find the right people selling the type we want. If we ever want to change our speciality license we just have to spend 10 gems to do it.