I really like this idea. It’s a generalisation of my desire for an uncle! button, consistent with the GTBee idea, and puts more control in the hands of the user.
Aside: I worry somewhat about folks being too aggressive with their deadlines, but that’s the same problem we have convincing people to be slightly less aggressive with their goal slopes. After a few self-inflicted derailments, they/we find a balance that helps us achieve more in/with our lives.
I’ll see your arbitrariness and raise you a theory: it’s always arbitrary unless there is a real-world reason for that particularly deadline. e.g. garbage night, end-of-work-day, etc. In some cases that arbitrariness feels helpful. Other times we become too, too aware of the games we’re playing.
I sure can’t predict in advance how I’d like my goal deadlines to be staggered across any given future day. But I might have the presence of mind to force myself to get things done earlier on a particular day.