The Herald have recently done a series of articles about Scotland's Railways and published an article by rail engineer and YouTuber Gareth Dennis with his view on where new rail lines in Scotland could/should be in the future.
View attachment 174304
Rail expert Gareth Dennis reimagines the future of Scottish railways. Here is how it could look from the Highlands to the Scottish Borders.
www.heraldscotland.com
He also did a video going into more detail on these proposals:
Certainly they are ambitious proposals, however I'd be surprised to see any of them built (certainly in the next 25 years) with perhaps the exceptions of possibly a line out to Fraserburgh and an extension of the Borders Railway to Hawick.