I love this idea. It really instills that minimalist Swedish inspired design that Massimo Vignelli was famous for. I do think the design needs some help though.
First, you need to do something about the white "stops" icon. Right now, it's very ugly. I suggest referencing the iconic Vignelli subway map from 1972. Maybe the dots aren't black, but white—just contained inside the lines so you can lose that nasty stroke. The one you have now just doesn't do this design justice.
Second, you need another design element. More nostalgia. How about some custom legends? I'm thinking metro icons, or borough names. Enter, shift, backspace could turn into Manhattan, Queens, The Bronx. I don't want you to get away from the clean look you're going for, but I really believe it needs some extra flare.
Lastly, another idea I have; what if you had the modifiers or alphas as an off-white or tan color? Sort of like the rivers on the referenced map are. I think doing this would add some needed contrast.
If you're interested in collaborating, I'd be willing to lend my hand—as I'm very interested in this project! Great idea!