I'm sure there's a business for some entrepreneur who could do custom and semi-custom water containers and water bottle cages and mounts, and maybe a few unusual but non-custom ones too. When we were riding the tandem a lot, and long distances, I was wishing there were a way to put a long water tank under the oval boom tube. I imagine it holding no less than 5 litres, and the CG would be as low as you could get it. In the west there's a lot of riding where you can go many hours without seeing anyplace to refill, no stores, no houses, no streams, and maybe not even see another human being for hours. On my carbon-fiber single bike, I would like to at least be able to mount another water bottle under the down tube.