Unai,
We discussed this proposal and would be happy to accept this contribution, although with a few modifications from what is described above. Details can be found in the design meeting notes here: http://entityframework.codeplex.com/wikipage?title=Design%20Meeting%20Notes. Let us know if you have any additional questions.
Please remember to follow the instructions for making a contribution (http://entityframework.codeplex.com/wikipage?title=Contributing). In particular, we will need a signed CLA before we can accept any code, and please don't forget to write tests.
Thanks,
Arthur