Create a WordPress-plugin for document sharing

We need a Wordpress plugin that allows sharing of documents between users, by the following scenario: User A uploads a task that includes a document with a description. A reward is calculated from additiional data the user entered: number of pages (1-1000), difficulty (1-3), level of service (1-3). The reward is attached to the document, it's in a virtual currency ("points"). Also, user A can select how many users may apply for the document. If level of service is "3", only one user can accept the task. User B sees the description and the reward. He applies for it. After that, he can download the document. If maximum number of applicants us reached, the task is closed. User B reads and edits the document. He uploads his new version to the task. User A views the new version and may either accept or reject it. If he accepts it, user A gets the reward (in points) credited to his account. If user A rejects it (he has to give a reason for it), Admin gets notified. Admin has the final choice to accept or reject the document. If Admin accepts it, user B gets the reward. If not, user B gets no reward. The reward always gets subtracted from user A's account. User A's account might go into negative points in the process. Important: User A can only _start_ (upload) a new task if he has a positive point balance in his account. If a document accepted, user B also gets a number of "experience" based on size of document, service level and difficulty. This way, users who do more work get more experience. All users may buy points via Paypal (exchange rate must be configurable). Also, Admin can give points to the users. Users must be able to see their own points in their accounts. Users must be able to see the experience of other users in the user listing. There should be a nice looking page / listing of current (open) tasks where all users and guests see description, difficulty, level and reward. Only registered users can apply though. Documents might be any file type. No need to be able to read them on the site. The plugin should inherit styles from the theme of the site. It must be compatible with Buddypress / bbPress that will be used for user communication. It may use parts of Buddypress / bbPress (not necessarily) or extend Buddypress / bbPress. Plugin should be localizable via standard WordPress mechanisms. It should not change core functionalities. You may sell the plugin to other users afterwards, we do not need exclusive access.