Thanks. I will let you know my inputs.

http://oxwalldev.blogspot.in/

http://oxwalldev.blogspot.in/2015/03/oxwall-plugin-development-user-rewards.html

Following features are completed:

    1. User Rewards Widget

User's View
    1. User can see current reward points offered by the system.
    2. User can see his/her earned reward points history.
    3. User can submit a request for redemption of his/her points against the redemption options provided by the system.
    (a) Handling case If user's current points are less than minimum required points.
    (b) If user has sufficient credit balance, he/she can submit a request to redeem.
    (c) User can view the redemption history.
    (d) User can cancel the redemption request.

Admin's View
    1. Admin can update the default credit values attached to each actions.
    2. Admin can view User's activity Logs and rewards.
    3. Admin can add options to redeem.

Planned:
    1. Admin receives approval notification on submission of redemption request (similar to user joining approval). Once approved, points would be adjusted and system will reflect the redeemed points in history.

 Advanced:
    1. Level and Badges management by Admin
    2. Notification to friends on up-gradation of Level and getting new Badges
    3. Leader-Board Widget

Thanks for the encouragement.

One way of helping could be by performing the testing to mature the plugin. 
(1) Install on your local setup.
(2) Tryout the plugin as User.
(3) Tryout the plugin as Admin.
(4) Report if any issues found.
(5) Suggest if any interesting idea/feature missing.
(6) Suggestion to improve current User Interface.

"User Roles".

I am trying to understand the possible correlation among credit,"Account types" and "User Roles".

Some examples would be helpful.

Preview is available Here

It is ready for testing. If interested to help in testing, please let me know.

It is in good shape (Basic version is completed). If you interested to volunteer for testing, please do let me know..