would be difficult. Western Ghats are horrible places to construct railway lines, which is why KR will go down in IR's history as its greatest engineering feat.
elevated route would be exorbitant, and besides moving heavy equipment in place and creating embankments while constructing will negate the whole purpose.
The length of the line proposed is a bummer though, should have been less; it seems a wasteful expenditure just to appease people staying in the region rather than well though out investment.