I was planning on making these exact parts, which is why I already have some of this set up. But this is how I would do it.
The part should a FGBuildableFactoryBuilding, set up as a lightwieght, using FGGenericHologram. This will give you the most snapping options on walls and foundations, catwalks, ect.
There should be a single plane mesh, uv mapped to 0-1, using a material similar to this one. The index changes which pattern is being used. You could make individual material instances for each part, using the correct index, or you could try to set this using custom data (preferred but would probably require cpp since pattern ID's are ONLY applied to FGBuidableFoundations). The material itself is in the Deferred Decal domain.