Defense for Japan is never a problem. There is a difference between stops the ball from hitting the floor and digging to use for attack.
Blocking is a problem. Attacking with shorter players is a problem.
Japan has never been about the middle and hence the left side of the nets where they attack from. If you know where the ball is going then it is much easier to set up the block and the defense.
If the setter is in the middle of the court when in the front row, at least the opposition has to decide which one to focus on. Plus still giving the back row a chance or even the setter dump. May suck on the blocking, or only use it on the first ball and then shift.