With the addition of the hole tool it brings new possibilities to us terrain developers but one key restriction is the fact that the water is still below the terrain which makes the hole tool quite useless in some areas of a map depending on height of terrain.
the feature i would love to see added is the ability to select a tile on the world and have a selection box for water in it so you can use the hole tool then select the tile and turn off the water to stop the player being in the invisible water which they currently experience