Regardless of how messy the process may be, these experiments have still made beneficial contributions to core. I do agree that the process needs some refinement. Let's hope the recent rush to get some features in core will not usher in unforeseeable issues down the road. I think the model is certainly good and its implementation needs attention, as you mention.

The link you included to Make WordPress Core does show planning for the 4.2 cycle, but I don't see specific work toward improving the framework and process for featured experiments. The guidelines/requirements set forth by Ryan Boren seems like a good start, if adopted. What other first steps could be taken?