I think it would be interesting depending on how fast mods are hemorrhaged. If the majority of the large subreddit moderators left overnight it would be very difficult for their shoes to be filled. It takes a different skillset than moderating smaller subreddits. The transition period where the new mods learned how to deal with it would be rough.
If the bottom fell out overnight it would also spark outrage amongst the users. If it was slower the userbase probably wouldn't notice.