It strikes me that it's not necessarily a bad thing if people are, right now, posting articles faster than they could sustainably produce in the long term. One thing you could do is not necessarily promote things immediately after they're written. Stuff on LW should still be relevant a week after it's written.

If there's a buffer of good posts waiting to be promoted, then we could make the front page a consistent stream of good articles, as opposed to having to promote slightly lower quality posts on bad days, and missing out on a few excellent posts on fast days.

EDIT: Another reason to wait before promoting things is that the goodness of some kinds of posts might really depend on the quality of the discussion that starts to form around them.