Decreasing playing area seems to be like an incurable disease at the moment. The easiest way to increase stadium capacity is to reduce playing area to put in extra spectator seating and the easiest way to stop delays of the games because of player safety (missiles being thrown) or spectator rubbish laying on the playing area is to rope off the playing area. I dont know the solution possibly the ICC could set a minimum playing area for international contests, but the downside to that is it knock a few current venues out of the running.
But if they ignore it the feilding team may risk becoming virtual standing room spectators.