I wonder if conditional due dates is something you have considered adding as a feature? I often have task that are depended on when preceding tasks are completed. One example of what I’m thinking about:
“Wait for comments from client” is a task, and once I’ve got the comments, I’ve seven days to update the web site. What I would like is to set the due date for “Send updated site to customer” to have a due date automatically set seven days from whenever “Wait for comments” are marked as done.