Setting a start time to freestyle games would end the advantage gained by the last player who enters - (s)he always goes first while the others are probably asleep.
The start time could perhaps be set by the person setting the game up?
It would make freestyle more attractive, then more people would take advantage of the quicker games you can play (i.e. minimum one turn each per day, as opposed to sequential where you might get one turn every six days!).