Incidentally, I think 18xx has been going through a mild resurgence as board gamers graduate from the economic Euro-style games and into the rules-heavy games, eventually becoming curious about this 18xx genre. It's been creating a bigger demand, and as such, many 18xx titles are getting reprinted commercially, instead of the traditionally hand-made variety.
https://medium.com/grandtrunkgames
https://www.kickstarter.com/projects/1840vienna/18magyarorsz...
https://www.gmtgames.com/p-847-1846-the-race-to-the-midwest-...
https://www.gmtgames.com/p-692-1862-railway-mania-in-the-eas...
I never really figured out how the operational aspect of the game should work, though.
You might like the book Design Rules: The Power of Modularity. https://www.amazon.com/Design-Rules-Vol-Power-Modularity/dp/...
I'm going to ponder how to design the game artifacts.