Drafts sort of server the purpose of a ready to publish/work in progress piece.
That is to say, you can keep your drafts behind the scenes while you publish other articles and when you're ready to publish it you hit publish.
I don't think your idea is stupid, but perhaps you need to make clear what your aim is. What do you think an additional form of post would assist with?
I'm in a simialr position, in that I have about 300 or so posts that I need to publish by copying and pastinfr one setup to another. I have several articles in the drafts section, and place them until I am ready to work on them. Then as I work on each one, I publish them when I'm happy with it. I think organisation is the best way to manage this, because if you think about it, do you think your backlog will t revert from drafts to ready to publish instead? In which case you may need a "Defintely ready to publish" post type:)?