We're unlikely to increase the water generation of the Face of Flow because everything in game uses up some resources. With active items like Faces of Flow they use up a lot of resources. If there are more of these being used, or they are modified to put out more water, this increases the server resources they take up. That would negatively impact the game in a profound way.

We didn't really add those to the game for the purpose of allowing people to turn Cornerstones into fishing ponds. Use them as an accent and they work great. If you want to fish there are tons of places to go all over the world.