Would you consider adding proper railroad switches (T-junctions) that actually show the direction they are set to?
Also a nice buffer (railroad end block) that transmits a redstone signal when collided at the opposite end, and still allows normal signal when used with a button (so it can be used both for detecting arrivals as well as 'launching' a cart).

Junctions are planned, yes. Not so sure about the buffer block, at least, in the way described.