Implementing a mod to vanilla minecraft just because it looked "pretty" or seemed "realistic" is a bad idea in general. First, implementing this into the game would take AGES due to the amount of time debugging and adding new things to the mod would take since all of it is of such high quality.
Secondly, how do you think the modding community would react to this getting implemented instead of a much more useful or simple mod? Mod devolpers would be outraged that this mod, with its uselessness and little appeal to the general community, would be fit to be added to the game. Currently, RoW is practically useless on just a singleplayer survival world, and only servers with a large playerbase would find a real use for this to improve their server's economies and transportation methods. Plus, the only people that would be thrilled to have this implemented would be railfans and kids looking for more ways to kill each other. For a mod to be sucessful when implemented into vanilla minecraft, it must not only have a certain usefulness, but also appeal to most, if not all, of the community.