Here is an example of VB script by Laurent DELRIEU for joining quite smoothly extrusions (minimum of 4). He used circles and rounded rectangles as profile for extrusions, but other shapes could be done too.
These shapes are put on the vertices of a convex triangular mesh. The axis of the extrusion is oriented toward the average of the vertices of the mesh. At the moment the meeting point of the extrusion direction must be inside the convex hull of the vertices. The script generates a BREP not a mesh.