I had no idea this was possible!
Since my copy of Illustrator is ancient, and I don’t want to buy an Adobe sub, I am investigating Inkscape for SVG making. The ability to make extensions, and to script it on the CLI is super useful.
SVG is a pretty readable file-format (it’s just text) and object styles are hierarchical, like CSS (you can in fact embed SVG in CSS and other HTML objects) so like @paulw points out, you ought to be able to programmatically apply a change to an entire line weight. Such a script wouldn’t even need Inkscape to work. That’s like a sed one-liner.
I don’t think changing the line weight makes any difference to the cut. I think it cuts down the middle. To adjust kerf you need to change all the endpoints to make the outline bigger if it is outside and smaller if it is inside.
It could be done with Python and Clipper but certainly not a sed one liner.