Can caesar export in dwg (or dxf) in 3D, showing routing and supports? if yes, how? (i think not using isogen because it export only in 2D).
the idea is export the 3D routing with supports so that 3D modelers can import the drawing in 3D model (as graphic, superimposed to the model 3D pipe ) and "see" support position.

No to both.
DWG is a proprietary Autodesk format, but DXF is open and ascii, so it should be reasonably possible to code a CAESAR to DXF converter.