Currently the preview displays the print head as a simple cylinder with a cone at the bottom. It would be helpful if that model could be replaced with an .stl file of the print head.
Having an actual model of the print head in the preview would make it possible to visually check for collisions during sequential printing.
The origin of the .stl print head file would be the tip of the nozzle. The X, Y, and Z axes of the .stl print head file would all be oriented parallel to the printer's X, Y, and Z axes respectively.
Many CAD/CAM software packages within the subtractive manufacture world have this feature, it would be great to see this become a standard part of Simplify 3D.