I'm aware that this is a rather broad question, but here it goes anyway...
What is, in your opinion, the most practical way to create own C# implementation with minor additions to the existing 4.0 feature set?
For context: I'm thinking about adding a couple of (mostly syntactic) niceties to the dynamic feature set that would improve the whole duck-typing experience. For example, these would include the idea of a dynamic interface, as proposed in this debate (particularly in the last comment from MiddleTommy).
I'm aware that nothing is stopping me from simply diving into the Mono sources. However, I'm compelled to first ask about potentially similar projects that may already exist in the wild. Any such extension efforts underway?