Summary

First, thank you Daniel for this amazing work.
I'll try to modestly contribute to this project, beginning with this remix of the round tower.

Extended and enlarged gate.
4 windows on the first floor.
A second floor with removable roof platform.

OpenSCAD Code

OpenSCAD code (Add in castle-kit-1-8.scad & doblo-factory-1-11.scad needed) :

module tower_round_2 (){    $fs = 0.1;    $fa = 4;    // Size of lego's caracters : 50mm/3.2mm = 15.625    solc = 15;    //          (col, row, up, width,length,height,nibbles_on_off)     base_plate  (-4, -4, 0, 8, 8, 1, false);    nibbles (-4, -1, 1, 8, 2);    nibbles (-2, -2, 1, 4, 1);    nibbles (-2,  1, 1, 4, 1);    nibbles (-4, -4, 1, 1, 1);    nibbles (-4,  3, 1, 1, 1);    nibbles ( 3,  3, 1, 1, 1);    nibbles ( 3, -4, 1, 1, 1);    difference () {    // tower structure    union () {        difference () {        cyl_block (-4, -4, 1, 8, 8, 46, false) ;        // carve it out        cyl_block (-3, -3, 0, 6, 6, 48, false) ;        // holes in the wall on top        block (-6, -1, 42, 10,  2, 8, false) ;        block (-1, -6, 42,  2, 10, 8, false) ;        }        // platform on middle        difference () {        cyl_block (-3, -3, 13.00, 6, 6, 6, false) ;        cyl_block (-3, -3, 12.99, 6, 1, 5, false) ;        }        nibbles (-2, -2, 19, 4, 4);        nibbles (-1, -3, 19, 2, 1);        nibbles (-1,  2, 19, 2, 1);        nibbles ( 2, -1, 19, 1, 2);        nibbles (-1,  2, 19, 2, 1);        nibbles (-3, -1, 19, 1, 2);        // block for platform on top        difference () {        cyl_block (-3, -3, 29.00, 6, 6, 8, false) ;        cyl_block (-3, -3, 28.99, 6, 5, 9, false) ;        }        // platform on top        translate ([0,60,0]) {        cyl_block (-2.95, -2.95, 0, 5.9, 5.9, 1,   false) ;        nibbles (-2, -2, 1, 4, 4);        nibbles (-1, -3, 1, 2, 1);        nibbles (-1,  2, 1, 2, 1);        nibbles ( 2, -1, 1, 1, 2);        nibbles (-1,  2, 1, 2, 1);        nibbles (-3, -1, 1, 1, 2);        };    }    // doors, uses a "house form"    house_lr   (-5, -1.5, 0, 10, 3, 13) ;    // windows    house_fb   (-0.60, -5, 23,  1.2, 10, 6) ;    house_lr   (-5, -0.60, 23,  10, 1.2, 6) ;    }}

PS : It's my first experience on OpenSCAD so the code can probably be improve.

castle-tower_round : 2 floors