I find it a bit annoying that I can't resell resources that I have traded for. Like having a resource then getting the same one from a CS, the additional resource is next to useless. or getting a lot of some strategic resource in a peace deal, there is no point to it unless I am actually short of the resource. It would be great if they could implement reselling resources that I have traded for. There would be some complications but I think it would add another layer to the game that could be fun.