Adding a commit message to the index

Is it possible to add a commit message to the index, and have it used as the final commit message, or as the template for the final commit message?

Witnessing AKPM's ongoing efforts on linux-kernel to get better commit messages out of people, it seems it would be beneficial to be able to stage a commit message and refine it over the course of the development of the commit. The first cut is rarely the best, so being able to refine a commit message as one can refine a commit by incrementally using the index seems like a good idea.

I know I can use git-commit -F and store my commit message outside of git, but it would be nice to have it in the index with the code it comments on. That would make the commit and the message stay together with git-stash for example. Apply this to other index-modifying operations too.