So I just went down a random google rabbit hole... had an idea for a future build, folding cargo bike, so I figured I should google it as I am sure someone has made one already. I stumble across a cargo bike company in france making modular cargos named Douze Cycles. They came up with a really nice solution for the steering allowing lots of turning angle on the wheel and its very clean. Plus being flexible it will allow you to get around problem areas when building those low slung stretched bikes. I am still unfamiliar with the terminology of those styles of rides. Looks like cables are replaceable, so sourcing them should be possible, I wonder if you can get a set of the pulleys as well? Or make your own setup with braided steel cable from the hardware store?
https://www.douze-cycles.com/en/the-concept/
https://www.douze-cycles.com/en/the-concept/