First of all: interesting game. It is very relaxing to build a small track, to place objects and also the "mission mode" is already playable.
I bought the game on Steam and as far as positively surprised :).
Here are a few questions and possibly ideas:
Will there be a steam workshop? Especially for own maps, missions and objects this would be perfect.
What about several trains, both solo and possibly multiplayer?
Adjustments of objects (color choice for different object levels).
An "automatic" mode, where the train departs via signs / traffic lights / switches, certain rods automatically.
Other vehicles, such as wooden cars, with associated road sets.
Dominoes, marbles, switches, etc .. to make small Physic-plays.