novel
But all the reasons you give could be accomplished just as easily after the novel has been published. It could even be done easier and better after the novel has been published.
One novel a year is average, not terribly prolific. But even at that rate, I still think it would be much like watching grass grow, if done in real time. Both Rice and King actually write far faster than the release schedule of their novels, and you probably wouldn't like seeing their first drafts nearly as much as you think, and you'd probably learn almost nothing from them except how well these two writers do the job first time through.
As for novelists being artists, okay, if you say so. It's a tag I'd rather not have placed on me until long after I'm dead and can't object, but okay.
But have you ever watched artists on PBS? There's a reason they almost always do paintings that can be done in half an hour. Do a painting that takes three weeks and viewers eyes glaze over and they flip the channel in search of something more exciting. . .like a city council meeting.
Better, I think, to do this after the novel has been published when all the drafts and changes could be posted in quick order. It would give just as much insight, would teach just as much craft, and do without boring most people to death. I don't think this has been done by a professional writer, but it's been done by bazillions of amateur writers.
I don't think X-raying the paintings of old masters is a fair comparison. They painted over other paintings, and aren't around to talk to. Writers don't type over old manuscripts very often. If you want to see the first drafts of a writer's novels, many are available hither and yon.
Lawrence Block even sells manuscripts on EBay. So do some other writers.
I've seen the first drafts of a number of pro writers over the years, and as often as not, the only real difference between first draft and published novel is some tightening and just a bit of polish. On occasion, there's no difference at all, or the difference is whatever the editor does to it after the writer hands it in.
In fact, I think I've seen more new writers discouraged by looking at first drafts than I've seen new writers encouraged. The main conclusion, the discouraging conclusion, many draw from looking at a first draft is often how well the pro writer writes, and how well the novel turns out first time through.
I'm sure there are some pro writers who turn out bad first drafts, but I haven't personally seen one. Generally speaking, if you write well, you write well. I could name at least two highly acclaimed pro writers who write only one draft. One of them, acclaimed for how literary his writing is, doesn't change a line of his first drafts. What you see in first draft is what the reader gets in published novel form.
For this to have any benefit, I think you'd have to find a writer whose first draft is radically different from his final draft. Even then the insight would apply to only that one writer. Writing is always writer specific. What you learn by watching one seldom applies to another. And likely doesn't apply to the new writers reading it at all.
Even then I think it's unnecessary. There's nothing you could see with a novel written in real time that you can't see after the fact, if the writer saves the various draft stages, and a great many do.
I also think you might be getting into quantum mechanics here. Quantum theory tells us the very act of looking at something changes it, so we can never see anything as it really is. By watching the writer write the novel in real time, you're changing the process, changing the way the writer does his job. You will also probably change his thinking process, everything. He knows he's being watched, and this can't help but make changes.
It might be an interesting experiment, but I doubt it would ever be a realistic one.
Many writers, probably most, do save all the drafts of their novels, and I think this gives a much more realistic picture of the writer at work than watching him write in real time would. Many writers also keep daily blogs of novels in progress.
Analyzed as it's created, message boards to discuss it? Sounds like prime reasons not to do it, to me. That's the last thing I can imagine a writer wanting, and the last thing any novel needs. This, in fact, is precisely why I think a writer would be nuts to go through this.