Hi knightxor, I just made the converter program, you can download it from here:
http://moi3d.com/download/Obj23dmWireframe.zip

Unzip it to some folder, and then you can run the Obj23dmWireframe.exe program.

It will prompt you for the name of an OBJ file, and then the name of a 3DM file - it will read all the polygon data from the OBJ file and convert the edges of polygons into line segments and save those line segments to the 3DM file. You can then load that 3DM file into MoI.

So this gives a method to bring the wireframe outline of polygon mesh objects into MoI to use as construction guides.

I hope this helps, and please let me know if you run into any problems.

- Michael