I like the idea of a supplement!
The things I'd look forward to the most in one would be: advanced rules to further distinguish each Nomad type from one another (perhaps each gets their own unique ability), a new Nomad type or two (one idea I had was some sort of Scrapper who builds stuff like drones and gadgets), more tables, and perhaps some general roleplaying tips or action/dialogue prompts for the different Nomad types (a little guidance can be super helpful when one is drawing a blank!).
Really love this game, and I'm excited to get the physical copy in the mail!