I've upgraded several residences and have 2 of 3 needed items to expand storage but I'm running out of space. There needs to be a way to sell either to city advisors via bubbles or in the global trade center or at least clear un-needed items if for some reason you are not ready to allow selling of items.
This is an interesting addition to the game but its going to ground players in a hurry since there are at least 10 different items and only 15 storage spaces to begin with and obtaining the right combination will be difficult or impossible once the wrong items have been obtained. And since it appears to be totally random what you receive from your research there needs to be a way to off load un-needed items.