This is a nice way to show what you can do with Postfix. But if you actually wanted this functionality, it would be much less error prone to implement this in y

This is a nice way to show what you can do with Postfix. But if you actually wanted this functionality, it would be much less error prone to implement this in your delivery agent rather than your transfer agent. For example Procmail or Sieve or whatever you use to filter incoming mail. (An email system is normally in three parts, a transfer agent that talks to remote systems such as Postfix, a delivery agent that delivers to a local mailbox such as Sieve or Procmail, and a user agent which is what you use to read your mail such as Thunderbird or mutt.) Just change your filter to change the delivery mailbox to a separate one for weekends. That way you won't risk causing any bounces if you do something wrong.