I vote for both plans at once!

1) Make the current LW read-only. All content is still accessible, but commenting and voting is disabled. The discussion section is closed as well. Let things rest for a month or so.

2) Announce that during the next year, LW will have one post per week, at a specified time. There will be an email address where anyone can send their submissions, whereupon a horribly secretive and biased group of editors will select the best one each week, aiming for Eliezer quality or higher. The prominent posters you've contacted should create enough good content for the first couple months. Voting will be disabled for posts, and enabled only for comments. There will also be one monthly open thread for unstructured discussion.

I don't think anything short of that would work. LW's problem is the decline in quality, so the fix should be quality-oriented, not quantity-oriented.