That sounds like a fun project you are starting on!
I think it would be appreciated by the forum members if you presented screenshots and the story behind directly into this forum. I think there even is a board for stories (here: http://forum.simutrans.com/index.php?board=59.0
If you like Discord as well, you can post on Discord and then link the images and copy the text to the Simutrans Forum!
Also, since you probably know that the game is evolving quite alot currently, make sure to keep lots of backup, since a save with a new excecutable might accidentally corrupt the savegame and render it unusable, and that would be a disaster if the save is well developed.