I think the Global Trade Market needs two things in order to be much better: 1.) A "Trade for" feature when offering an item. 2.) A search function in the Market itself.
The "Trade for" feature would allow you to set what you want to receive from the trade. For example, if I had too much wood, but I needed more metal, I would be able to offer 10 wood for as much metal as I'd need, up to the point where the max value of metal being recieved met the maximum value of wood being offered (so that you wouldn't be able to trade 3 metal for 6 donuts, for example) and/or up to the point when the City Storage fills up. The Trade For... parameters could be applied to any commodities in the game, in addition to SimCash (up to 1 SimCash per 100 Simoleons of the item's value), as well as Simoleons, like it is now. You could also have several parameters, so that you could trade 8 chemicals for 5 metal and 3 wood, for example. And you'd only be able to set the Trade For... parameters as commodities you've already unlocked (so that a person that's level 7 wouldn't be able to ask for 3 watermelon, for example). So that's basically my idea for the Trade For... feature.
Now, my other suggestion is to implement a search feature into the Marketplace. That way, you could search for people with trade offers that match specific parameters. 4 minerals in exchange for 2 shovels, or 5 security cameras for up to 500 Simoleons, for example. This would make the trade offers available much more organized and helpful, and it would make the Marketplace as a whole far more useful.
These are just ideas, so if they were to be implemented, EA may change them a lot, very little, or not at all. I'd just love it so much if these two ideas were put into the game.
