Yeah, convincing the fat guy to be a hero is a good option, but would be good to try and find large enough objects to replace him first. Other good options would be flipping the switch on-off fast or precisely enough so maybe the train derails (would need to know if it’s a freighter and the speed/terrain config). I would also hunt down those who tie people to tracks, and those who sabotage both normal and emergency brakes or intentionally direct trains over people tied to tracks.

PS. #3 and #1 is not the same, in #1 the ’alterative’ has no choice, in #3 you can talk to the fat guy which opens a whole slew of other options.