Ability to set time limits on each project or folder instead of only due dates.
For example, I've got project X and for project X I only want to spend 8 hours per month working on the various things I need to do. So I set the project time limit to 8 hours, then I get to work.
As I'm working and logging my time, I get notified as I'm nearing the 8 hours, or this is shown clearly within each ticket overall time spent on that particular board.
This would allow us to work until the billable time, and easier to not go over retainer costs.