If you look around Grasshopper-land, you may find some tool-path generators. There was one that did 5-axis, that perhaps be dumbed down to 3, err 2.5D.
I’ve used LinuxCNC for running my machine, and I was looking into PyCam, though their development stopped, which is a shame. Because it’s just Python, it would seem that something like PyCam could be implemented in Rhino, perhaps without threatening the makers of many fine tool packages, well not really for the last part.
FreeCad also has some CNC ability. It imports Rhino Step files just fine. It’s very left-brain and tedious to draw in, for a Rhino person.
Nudge: I wish there was an entry-level CAM solution for Rhino3D - #10 by Brenda