That’s a pretty good use of offset. it works very well for some designs, but others not completely.
I haven’t been able to get Inkscape to render offsets for precision work in making inlays and relieves. The green eye is a good example of difficulty in using offset on a piece with complex outlines, especially with both convex and concave parts. I use stoke width and then stroke to path to get snug inlay pieces. You might try that for the eye.
Here is a link to an old topic that addresses some of these workflow issues. I got lots of ideas and help from the community, especially from @Jules for using stroke to path and @palmercr to show how OpenSCAD would do it. @dannyc’s post inspired by someone not on the forum though really fit my needs the best and allowed me to efficiently make inlay Scrabble letters.