I can't see what reducing the time of each half to 40 minutes will achieve.

If the ball is out of play for say 10% of the game, that's four and a half minutes. So if we reduce the time of each half to 40 minutes, and the ball is out of play for 10% of the game, that's four minutes. So do we then reduce the game to 35 minutes?

What is required is good time keepeing by refs, or as someone suggested, an independent time keeper.