Zoomable line widths?

The only line widths I know of on Rhino are:

(1) Print Width settings in the Layers palette, then viewed with the viewport Print Preview option included.

(2) Viewport Display Options that can be also individually assigned to objects.

But both of these fail to set a model-space line width since they only determine how thick the lines are on the computer display no matter what view zoom settings I’m using. The lines thus become too fat and clog up the model when I’m zoomed out.

The (1) settings do export correctly into Illustrator .ai or Autocad .dwg files, but I get no valid preview of this within Rhino.

My option seems to be some Grasshopper aid to overlay line previews based on Print Width settings, quite a task that may bog down with highly complex models.

I guess Rhino isn’t a very good replacement for Illustrator? All I need is a useful WYSIWYG preview to help me create proper line widths. Setting the view zoom to 1:1 is a kludgy option I’m not sure will even work well, and won’t ever let me zoom in either.

I also need SVG export, so I’ll be in Grasshopper anyway, going that via Python.