I imagine the tiered hardscape to be easier to make with layered poly sheet. You could also give it very nice contours with that kind of construction.
I plan on buying a sheet this weekend and playing around with making shapes out of it, I'm looking for a pool with low lying crypts on the edges and a small rock in the middle with a couple species of Buces on it. All the bare surfaces will be covered in aquatic mosses and the whole thing will be misted regularly with a mistking system. Flowing water is less important to me than the illusion of pool with crypts growing on the banks and some buces clinging above the water line. I have the vison in my head now to make it reality. I just increased my Buce collection and I think they really need to be showcased.