Came across this a while back:
which was mentioned at: http://forum.openscad.org/OpenSCAD-carving-feature-for-CNC-milling-machine-td14136.html and http://www.mattvenn.net/2013/02/17/using-openscad-for-2d-machining/
May have to try it and see if it makes modeling joints of various sorts simpler. I’d be curious if anyone tried it, or had found some other similar thing which I’d missed (ironically, it comes up this morning 'cause it came up during a search and when I went to add it to the wiki found it already there at: https://www.shapeoko.com/wiki/index.php/OpenSCAD#Export_to_DXF_for_CAM_.28alternative_to_.stl.29 )