The only problem with using a program like simpose is that you are using what are effectively EA's meshes.
I'm not sure how actively EA would follow up someone using their meshes this way, but I suspect they wouldn't be happy if they found them being used in another commercial program, and I'm not sure Auran would thank anyone for uploading them either.
I could be wrong. 
 
I wouldn't recommend using scripted texture replacement either.
This could result in a big lag in FPS if a significant amount of the people were placed in one area.
I think it would be better to have a dozen or so models already loaded into memory and placed many times in an area, which we know trainz does best, and there would be no additional load on the CPU.
Incidentally, 

 , I've just spent an hour working on a person model.
The total polycount is 322, and it doesn't look like I'll have to add to that.
I spent a bit of time on the head, which is where I personally would like to see some realism, and the head takes up 100 of the 322 polys, but it's well worth it.
Here's a pic of the head with edged faces to show how easy it should be to skin:
		
		
	
	
Not bad for 100 polys eh?
I've still got some major tweaking to do to the rest of his body, and then I'm going to see how he looks in the game.
hopefully I'll have more pics to show sometime this weekend, and with a bit of luck the polycount will stay at 322.
Cheers,
Smiley.