GeoJSON for floor plan

While evaluating different technology to represent an office floor plan (so, basically 3d geometry data and 2d representation), I came across many new javascript package for client side representation.

I see suggestion to use openlayers.org, but afraid may be most of the features are not useful to me. I currently thinking about rendering svg model using d3js.org.

1. Is it worth the effort to learn openlayers? Would it make easier to render the floor plan from GeoJson?
2. Is there any benefit in storing the floor plan (coordinates + Height, Width, Depth data ) in GeoJson. I plan to use MongoDB and heard it natively support geoJson .Or is it enough to store the data with custom structure (class). I don't know much about GeoJson, and not sure whether the data needs to be geospatial. All the examples I saw so far is related to maps and not for geometrical shapes.