The 4Ps of Gunpla: Plastic. Practice. Patience. Pain.
After 20 hours of etching on 1.5mm HIPS (and, with painful hands and arms afterward), the ground pattern for the Dragon Ronin's shrine has finally "taken shape." I've "undertraced" the Dragon by attaching the print over the HIPS with double-sided tape, used a sharp knife to score deep enough onto the plastic, then later on deepened the grooves using a dried out microline pen like a stylus. For the Yin-Yang stones, I used a compass and a circle cutter to score the plastic, and used the same stylus to etch the details.
I had to shoot this at an angle to make the "stones" visible. The Dragon itself is visible because I've penciled in on the grooves.
Quick update. I've reinforced and cut the Shrine's ground design using a combination of hollow beams and 2mm HIPS. I've also made the stairs with 2mm HIPS and simply connected it to the main design.