Example of creating a cutout for a 3D object which is pivoting around the origin.

rotate_extrude3D.scad

module rotate_extrude3D(clearance, bounds=[1000,1000]) {
  rotate_extrude()
    intersection() { // clip to positive x axis before rotate_extrude
      translate([0,-bounds[1]/2]) square(bounds);
      offset(delta=clearance) // add clearance to profile
        union() for(a=[-90:$fa:90]) // union projections from multiple angles
          projection() rotate([-90,a]) children();
    }
}

difference() {
  translate([0,0,-10]) cube([100,100,100]);
  // assumes object is pointing along positive X axis before sweeping
  rotate_extrude3D(clearance=0.5, $fs=1, $fa=1) mything();
}

// View -> animate to show sweeping
%rotate($t*360) mything();

module mything() {
  union() {
    cube([50,20,2]);
    cube([50,2,10]);
  }
}