[steam for ever]

If Dinorwic quarry had not closed the Padarn would have carried on working.
In fact, all but one of the 4 stated were closed only because their work ran out and not becuase of gauge issues.
The one that did have the gauge changed to standard became GWR, so it was rebuilt to make things easier.

It would be incredibly expensive I agree, but the wierd and wonderful usually pay their way.
The southwold railway is being rebuilt to a similar style to this sort of thing, so it can work. Now a rebuilt GWR 7ft 1/4 inch gauge line would be nice, but that isn't narrow gauge.