texture procedures

recently I had an idea! what if I add procedures for displaying different textures? let's say instead of textures to put not a texture but a texture procedure, what do you think is a good idea? how does texture processing work? let's say if it's raining, then change the texture to one, and if the block is in water, then to another! I think it's a good idea, I would be very happy if you would add it!