Shipping (module/plugin/addon) <- for purchasing real objects, but you can build that into the price.
Paid Subscription / User Upgrades needs to be modified by an Administrator.
The cart system would only have one group [Register], then a new member would join as normal and have the option to purchase by money and or trade in trophy points or just use the default group and purchase at a later time. As the system stands, you can not customize your own option(s) and only select what has been setup for you.
Avatars (larger, animated, [board defined: not available])
Signature (allow image(s), more line(s), characters)
Forum Access (special area (pages), admin gen. Code, time limit access)
Profile Posting (allow images)
(Some things within the forum needs to be standard though out)
The cart system would let you purchase from a store front and not what you see in all subscription base forum(s). Just my thoughts, but would like to read/see another version....
mind you that this might make it a bit hard to import other forums, as they would need to follow this new method and or we follow what is here already...