The romhack ETC3 is a short entry, I think it took me 35 minutes to beat, and half of that was reading the introduction...
I'm not sure the game made use of the theme at all, unless the dialogs was related to an railway empire that used to exist and the broken railway was inspired by that? Maybe it went over my head, but the theme was never mandatory so is all good, and is not like I could make much use of it either.
As a FE8 romhack it doesn't deviate much from the base game, it has some stuff like split Str & Mag, skill icons to show mounted units having canto+ and other QoL additions.
The unique charm comes from the weird crossover of characters taking place on the short but crazy plot, even if some character like Yugi or Mario weren't actually playable. And the unique objective, to remove all obstacles from the way of a moving "train" pushed to keep advancing and pushing every turn, and there were some interesting enemy positioning to make the game more than just a "kill rush"
But there were some pain points, my first try was a failure because after visiting the first village and getting "beat the ballista so I can fix the bridge" the village closed and I couldn't trigger the repair. And then, I don't know if the guys next to the cracked walls were supposed to do anything or not... but they just stood there.
All in all, short, fun and with an interesting objective.