You can use %brick.setDatablock() to change a brick's type after you've planted it, but that can cause issues as bricks aren't supposed to change datablock after they've been planted. Your best option to do that is to delete the old brick and create a new one.
But, you seem to just want to scale something up, not change its datablock. Bricks can't be scaled so, unfortunately, you would have to use a static shape or create multiple different datablocks: one for each stage of growth.