1. how about a way to park trains without the No Route banner?
If the train contains at least one wagon that has a capacity, you can set it to wait for 100% load. Since it won't be loaded, it won't try to move to the next station and will never check whether it could, so won't find out there is no route.
It's possible to create invisible platforms and an invisible locomotive such that it looks like a bunch of wagons are just parked on a blank track with this trick.
2. How do I add Direct X models to a add on?
Simutrans requires images in png format. Any kind of 3D model just needs to be rendered as 2D raster images in othographic projection from the right angle. Those 2D images then might need some cleanup (removing unintentional special colors, cutting them up if they are larger than a single tile), which can be done manually or with tools like Shades and Tilecutter (
https://forum.simutrans.com/index.php/topic,20149.0.html). - for buildings, Tilecutter is especially nice, since it already gives you a barebone dat-file. The dat-file contains all information about the objects, eg. for a citybuilding a name, when it's allowed to spawn, how many people work/live there etc. If you look at the repositories of the paksets - eg. for pak64 (
https://sourceforge.net/p/simutrans/code/HEAD/tree/pak64/), I think the general idea becomes clear quite quickly - it's usually easier to start by copying what's already there. When you have both a graphic and a dat file, you need to combine them with makeobj (
https://sourceforge.net/projects/simutrans/files/makeobj/). Makeobj is a command line tool - for most new users that's something they have not encountered before, but I trust that you remember a pre-gui-computer era and can deal with it
Now of course this is just rudimentary "where to start" and I don't expect you to be productive from just that. I guess my first attempt, in your shoes, would be to try and bring your files into blender (
https://www.blender.org/). As far as I know, that should open DirectX models, but I'm not sure how well that works. pak128.britain has public blend files for comparison (
https://github.com/JamesHood/pak128.Britain-blend-files) and there is a script for automatically placing a lightsource and rendering in the perspective/angles Simutrans needs (
http://bridgewater-brunel.me.uk/downloads/render_SimutransRender_pak128Britain-65.py). Since I don't work in 3D, I can't be of much help with all that, though.
I think you shouldn't concern yourself too much with what comes after - that can be dealt with once you have usable png images. Perhaps it's enough work for one person to bring what you have into a blender format, and it makes more sense if others could render them out for the various paksets. Assuming your models might be american-centric TheRoadmaster1996 (
https://forum.simutrans.com/index.php?action=profile;u=12093) seems like a candidate for such a task, since he is currently working on an american-themed pakset. (No, this has nothing to do with you being 71 years old and claiming your health is crap, such that 7 gigs of material could be lost any day, why do you ask?)
Phew... hope I don't get flagged as spam with that many links...
