I would like to see a test drive function for the shop that you can drive the train once before you buy it, because if you like the train but can't ride it because it's too easy, that wouldn't be so great for the buyer.
I don't think that would work. I mean no other game has it where you can download a vehicle for free to test it before paying for it.
How would this work? What benefit would this be to those who buy a train but don't intend to drive it?
To be fair, there are plenty of "demo" games still out there. Maybe in this case DTG could make the Training Center the demo, and every time a new route/loco comes out the demo gets updated so you can try it there for free (with a limited playtime or some other reduced game feature set).
What about just watching the streams? Or if you don't trust them, find any youtuber and just look at the videos, so you can make up your mind?
If you are on PC/Steam you get two hours of play (the core game) to refund a DLC if not satisfactory. Subject of course to not abusing the feature. Otherwise as said, read the reviews, watch the (impartial) streams and make an informed decision.