Well I've always been wanting a MMORPG with an open-ended economy... For instance, like in World of Warcraft to make a sword you need so many iron bars, so many gems of this type etc... I want an MMORPG where if I want to make a sword i can just take an iron bar, a few gems of my choosing, and make a sword that is completley different than anybody elses. Thats an open-ended economy.
You could change the world of gaming with something like that!