Environment approvals will be difficult for such forest areas. Karnataka is struggling to get approval for Hubli Ankola line for decades.
Regarding Sabari line, instead of creating new new alignment possibilities, let the line from Angamaly start upto Ettumanur (via Perumbavoor, Muvattupuzha). If needed, a bigger town of Pala can be added with little deviation. Beyond that, it is doubtful.