If I understood you well you want to model in Shared Coordinate System in Rhino.
What about orienting the building preview in Rhino into Shared Coordinate System and do the opposite with the terrain points?
The first group will preview the Building in Shared Coordinates.
The second one will take the points in Shared Coordinates and will convert them to Internal Origin coordinates to place the Terrain at the correct place.
Do that work for you?