Trade resources in the market

Hi I would like to ask an implementation for trading other resources...

This game actually lacks a way to trade some resources for other kind of resources, it would be interesting if you can add a black market under the market building where everyone can put a trade offer

for example trading 1000 iron for 1000 stone, or trading X wood for Y iron etc...

Regards

Has been requested before.
Definitely needs to be implemented.
Maybe make it unlock at a certian level of the market? Right now there's no benefit to leveling the market.