I'm imagining a way to use solar power to grow hydrogen filled mylar cells at scale in a lake or ocean. You could organically grow an enormous platform as a skyport, e.g., elevator up the cable a couple km, then take off from there. Hell, maybe you need these skyports to support the business end of a massdriver.

https://en.m.wikipedia.org/wiki/Mass_driver

Images (and calculations) in the deck: https://docs.google.com/presentation/d/1r6CPFJ1AX1ZULacguTf6...