The only thing I've been missing from xenforo, is the ability to make certain upgrades available to buy only when user has some specific upgrade or upgrades. I would mainly be using this for making duplicated items with discounted price for users and for offering certain upgrades for people that have already gotten this exclusive upgrade. I managed to make this modification myself by adding an extra column to upgrade table, and by making a small extra check for the original php script. But the above doesn't have any kind of settings page for handling the "which upgrade is needed" for this to show, since I'm not capable of writing such a modification or add on for xenforo. In my opinion, lot's of users would have use for this extra option in the board.