-Alright, hear me out...
Obviously, Hisako needs to be a fully-articulated figure. But also no one wants her Armor to just be a static shell, either. So, you put swivel points in at all the necessary joints: neck, shoulder, elbow, wrist, waist, hip, knee, ankle. The torso can be split in two, with a clip for her waist on the inside of the back to hold her up inside. Then, you'd plug in the head & limbs. It wouldn't be completely articulated, and you'd definitely have to pre-pose her before putting her inside, but you'd still have her fully articulated, and the shell wouldn't just be a solid shell...