Volleyball timed would just be weird imo just because there are already so many natural pauses in-game. Like Basketball and Football, Handball, Hockey etc. its always ongoing whereas when at Volleyball the ball hits the floor it's over. I also had this idea a while ago but in Volleyball maybe it's weird.
Just imagine the time-wasting on a team with a lead...
Just cut out technical timouts completely, maybe speed-up the time inbetween point-serve just a little. I think that would be more then enough already. 2 TO's + 2 Challenged is enough breaks.