A learning model that I think is close to your desired one is as follows.
For example, I want to learn from Wikiversity to get my masters in Computer Science. I join the computer science group, and we collaboratively complete projects. The wiki's can be used like a source control application and it can automatically record what percent of the completed project each member has contributed. When a member meets a pre-determined percentage a degree is given.
For example, the CS group has two projects:
1.Create a mail client like Outlook.
2. Create a media player.
- If one member writes 52% of project 1, (s)he receives a masters.
- If another member writes 33% of project 1 and 20% of project 2, (s)he receives a masters.
This is a simplified example but a model that I think has potential.