Back in the late 90's I worked at a rolling stock maintenance depot. We were just designing new EMU's (Electric Multiple Units). The older slam door stock, such as the Class 411, were 30-40 years old and were to be replaced by the then new 375's. The old stock was in the 160 ton range for a 4 car unit. The weight saving per 4 car unit was around 25-30 ton, which is quite a consideration without also stripping out anything unnecessary. I also remember that some of the equipment, primarily the traction motors I think, were based on Swedish designs and they had a test train in Sweden with an old 411 carriage and new traction motors and brakes to use as a test vehicle. It ran on a short track and our engineers were impressed that it was got up to speed and safely stopped in such a short distance, even on icy rails.
This is the idea I was thinking of for coping with inclines
https://en.wikipedia.org/wiki/Cable_railway
I avoided suggesting a funnicular style as that is generally 1 carriage going down as 1 comes up, which presumes a regular passing of carriages in your world to make it work.