Which is what separates us from the animals.

Can you fillet unions? Like, if I union a cube with a smaller cube sticking out of its side, can I make a fillet so that the edge where the two cubes' faces intersect doesn't become a stress concentration point for cracks to start at? This is OpenSCAD's primary weakness from my point of view.

Quite easy to add chamfers to everything in the CAD file. But your manufacturing guy is going to strangle you...