Would love to see a Sydney route introduced. Hornsby via Sydney Central to Katoomba in the wonderful Blue Mountains would be my Number One choice. Others. Sydney to Newcastle (North) Sydney to Kiama (South) Bondi Junction to Cronulla and Waterfall.
You'll likely find most, maybe even all of those have some great proposal threads here: https://forums.dovetailgames.com/threads/australian-proposal-suggestion-master-list.41526/
Hornsby to Katoomba would be the longest route in the game by a massive margin, so something more like berowra-central over both the north shore and main north lines would be better. Same for Sydney Newcastle and Sydney Kiama. Bondi - Cronulla/Waterfall has potential though!
