Great idea, thanks for sharing. I'm going to put a bowl at the bottom inside the coconut fibers, fill the bowl with lava rocks and put a mesh over it so the roots don't go into the water that will collect there. Will keep them from drying out too quickly and give some protection against water leaking out the bottom. It could also help to make it keep that bottle shape and not get droopy over time.
Using a bamboo pipe and pieces of old fishing nets (non-plastic) would make this environmentally friendly. I'm thinking of placing these in the trees of our future home. Great idea!