My board game ideals

It sounds like you want a game like Cutan.
How hard of a game do you want? Is it a faimly game or one were only a few will enjoy?
I believe as far as a trade game goes think about the challange this week and have it a rock paper sizzor type were each trade type is greater than another and less then another and each is needed to buy property or advance your playing piece.

Well I think since you already have a good idea of some of the base functions of the game you should experiment with different themes to try to see which one fits best with what you're looking for and then go to mechanics from there.
I find a good way to get thinking about a game is to ask questions about specific aspects of the game and to see where your preferences lie. For example should the trade system have currency? Catan has no currency, you barter resources between players but I think most trade games have some sort of currency. Are players trading mostly with each other or with an external market? I'll use Catan again as a reference because I think it's a game that most people are familiar with and has some basic trading, in Catan you trade mostly with other players but you can trade with the bank for a much higher price. I suggest that if you want a high degree of player interaction try to make sure the players have to trade with each other as much as possible, a way to do this would to have a variety of resources that the players need to succeed but only give them access to a few forcing them to trade for resources they don't have with other players.
Another important part of trading is the movement of goods. Are your traders moving goods from one place to another, buying low in one place and selling high in another? This is where a board would come in giving players different routes to follow and different destinations to go to. You can also have static trading where the resource supply or market has natural fluctuations that make it so moving around isn't necessary. In Catan you are largely static but can gain access to new resources by building additional towns and roads, the resource fluctuation is given by the fact that you collect on a dice roll.
The cards chosen at the beginning of the round could be a way to specialize resource gathering. For example you could choose different roles based on what resource you want and since you could only choose one role you would have incentive to trade with other players. The problem might be getting players to choose different roles, this might be accomplished by making resources less valuable when there's more of them around, something that tends to happen naturally anyway but can be given a further push when you're designing your game.
I can't see any reason why the things your looking for would be in a war game, I think a trading game by itself is plenty exciting.
When it comes to customizable boards you can either set up the whole thing at the beginning of the game, again like Catan, or you can have pieces played throughout the game that has an influence on player descisions. The thing about customizable boards is generally I think it would be a good idea for all the pieces to be the same shape so that they can all be interchanged or at least to keep the number of different types of board components limited.
That's all I can think of, I hope you find some of it useful.