One of the most important features still missing in ModelConverterX is the ability to read in API macros that use lines instead of polygons. I have started working on a solution for this now. Those lines will be read in and then transformed into a 3D object. It is like you extra a certain shape along the line to get a 3D version. I will use a simple circle for the shape to extrude with, where the radius and number of vertices are an option the user can specify. By setting the number of vertices to 3 you would get a triangle to extrude, which costs the least polygons of course.
On the right you see a first picture of this feature. All the bars that form the arms of the crane are defined with lines in the API macro. But the tool has converted them into polygons that actually show up.
There is still some finetuning to do on the extrude functionality though, especially where the polygons of different line segments are supposed to line up with each other. But at least the basics are working now.