I don't know if this will work, but it sounds like fun.
It would be easier to designate game types based on days, though (Example: 1v1s Fridays, 2v2 Saturdays, FFA Sundays). That way, people in this thread can challenge people with everyone knowing exactly what day to show up. Also, it won't be a hassle for those who want to just drop into a match online. And yes, it should start at a certain time each day.
I think what would end up happening with time is that the format would change too rapidly for people to bother trying to schedule themselves into a specific one.