I agree that this is also a needed feature. I have over 3200 posts and my wp_posts table is so large that I can't even optimize or repair it using phpMyAdmin because my memory runs out. This is the only table I have this issue with and if there was some way to divide this large behemoth out into about 10 manageable sized tables, I think the entire site would run faster.
I hope a solution is found soon! :)