It is frequently suggested, and one very similar one to yours involving laying tracks between towns was also suggested, but I couldn't find it with a quick search.
My main complaint with all of the train ideas is that it just isn't necessary. What problem does it solve? On my slowest world (the one where I don't have a quarter horse, and no Indian's set, and no mobility), I can cross from one corner of the map to the opposite corner in 12 hours. Yes, that does take a little while, but could a train realistically travel faster than one and a half night's sleep?
Quests? A few class quests require a lot of travel, but they're supposed to be an inconvenience and the rewards from continuing the lines are well worth it.
Fort battles? Yes, traveling to a battle can tie up a lot of your time, but the XP is good and there needs to be some sort of balance (and paying for travel is not a balance. Money is easy.) I guess it would make it easier to harass towns or alliances that are several sectors away.
Duels? I've dueled in every sector of w1 and have no complaints about the travel involved. If you're a full time non-zero-motivation dueler, you need time for your motivation to get back up anyway.
Edit:
They do fit the theme of the game, but any train suggestion is going to be a lot of trouble to implement for extremely little gain. A very simple train station addition to the town would be a lot simpler, e.g. both towns must have a train station; click on the train station in the town you want to travel to; click "board the train" and the timer starts. Still unnecessary, but a lot simpler to implement.