In 2015 FIVB changed the rules of the game, specifically the size of the playing area. The free space behind the court was reduced from 7m to 5m. The stated reason was to allow more space for spectators.
I wrote about it at the time as it is in every way a ridiculous idea. Firstly, a smaller playing area reduces the space in which players have to chase down the ball and therefore decreases the length of rallies. Increasing the length of rallies has been the major goal of FIVB for at least as long as I have been alive (hint: think if a number greater than 49). Secondly, anyone who has ever been in a big stadium knows that space will never, ever be filled by spectators. As you can see in the photo above, the space between the edge of the playing area and the start of spectators seating is flat. Any seating that is set up in the space will have a terrible view and no-one will want to sit there*. In short the change is nonsensical and the reason illogical.
So this is my proposal. If you want to make rallies longer, the obvious solution is to make the playing area BIGGER. The more room the players have to run, the balls are playable and the longer the rallies will be. And don’t legislate the maximum size if the playing area. If you play in Krakow in the Tauron Arena (as a above) have 10 metres in all directions. If the stadium is smaller then you have less space, but still the maximum available. Crowds love it when players run a long way. Give them what they want.
*Thirdly (but don’t tell anyone), these huge stadiums are beautiful and impressive but hardly ever full for volleyball matches anyway.
Is there a rule for height of the roof? Surely not all stadiums are exactly the same height and players adjust to this. Your idea makes sense to me.
There is a rule for _minimum_ free playing space height, which is 12.5 m from the surface for FIVB, World, and Official competitions (or 7 m generally).
[Also, if I am not mistaken, the 2015 rule change was not 7→5, but 8→6.5.]
What about the suggestion that in future the serve player probably has to land behind the back court line producing a jump serve?
I think it is a stupid suggestion.