Well, before you can bring in MSTS content creators they have to like the game - I know most of the MSTS content creators, and they don't like Trainz.
1. Physics - that's the primary reason, and they're wrong about that, in my opinion if you're driving in CAB mode instead of DCC the Trainz physics can be just as realistic as MSTS, and in some cases more realistic.
2. Splined switches - consensus of opinion is that Trainz switches look like they were drawn on cardboard by a drunken gorilla with a broken crayon.
3. JET. From the very beginning Trainz was a jerky slideshow that didn't look half as good as MSTS, while at the same time not running as smoothly on midrange systems. All the tweaks and updating they did to JET over the years hasn't improved anything, for what it displays it still requires too much horsepower to overcome the constant jerk-jerk-jerk. Minimum and even recommended system specs are way too optimistic, I exceed the minimums for TS2009 by quite a bit and still get 10 to 15 FPS at medium settings because the coding is just plain clumsy.
So fix the last two, convince them that the first one is a myth, triple the sales and make MSTS extinct. I've been with the Open Rails dev team since the beginning, not because I think it's a great idea but because of my contributions to MSTS over the years and extensive technical knowledge of how that game works, but in my opinion it's a project that never would have been started if either Trainz or Railworks was an actual IMPROVEMENT over MSTS. They both do SOME things better than MSTS, when they needed to do EVERYTHING better and they fell short.