Hello Michael,

Position, size, shape, intensity and the ability to save/edit/delete lighting setup. I realize MoI isn't really intended for this sort of thing and other render tools can get close enough to cobble things together even though it's sort of clunky.

In thinking about it a bit more if you were you make the process interactive you could use sliders and/or numerical input to define a starting iso density, it looks like you have the ability to have the isolines retain continuity across surfaces, that's a good thing. Being able to group, join and merge lines that are connected end to end would be really useful as well, this enables the designer to determine the flow of the shading lines to give a different look to the drawing.

Being able to automate these sort of tasks would really speed up the process and if made somewhat interactive one could quickly iterate and clean up designs.