I originally posted this in another topic but I then I realized this board would be a better place for it.
I think Bobik should make a very limited amount of trading posts and they should be claimable by kingdoms and guilds.
That way for players to sell their items to the server they will have to pay some form of tariff to the ruling kingdom. This system would allow kingdoms to make them selves as accessible as possible to attract more trade into their nations and bring in an influx of tax revenue.
This would make guilds actually protect their lands from roaming bandits so trader players will feel safe traveling into their lands to trade with the server. And kingdoms that don't effectively patrol their lands will be avoided by traders and they will lose potential tax revenue.
This system will also make trade pacts actually mean something. So A kingdom without a trading post can sign a trade agreement with another kingdom allowing their citizens to travel to their land and sell their items. And if relations sour and the trade pact is dissolved it could be a provocation for war. I feel a system like this would add some more complex politics to the game.
It may seem a little unfair but hey, Life is Feudal
EDIT
There are also some other options to implement this:
1) Bobik said in the YouTube interview that certain grids have an infrastructure level based on the amount of development and quality of buildings on that grid. The Higher the infrastructure level a grid has, less wild animals will spawn. You could have a system where when a Settlement has reached a certain high infrastructure level with a wide range of different buildings you get the option to spawn one trading post within your city.
2) Another system could be a Guild level/tiers requirement. So when a guild has built the highest level/tier monument they can spawn a trading post within the city.
3) A third option could be a payment in real world currency for the convenience of having a trading post. While I'm not a fan of this option I understand that the dev team still needs to make money to keep the game thriving so this could be another potential revenue stream for them. This option however would kill the political aspect of my Idea for trading posts.