This is my interpretation of the Jyn's stormtrooper doll from Star Wars Rogue One. It's not 100% screen accurate, but it's close enough to be fun. I designed it to be approximately the same size as what's seen on screen. There are channels in the doll so that the limbs and helmet can be attached to the body with elastic cord and still be somewhat posable.
The helmet requires some post processing. This piece is probably the least accurate of the bunch, but the doll looks very "home made" on screen, so I think it's fine.
Since I don't have a dual extrusion 3D printer, and I couldn't think of a better way to do it without paint, I decided to free hand on the black details to the helmet. I did this via PLA welding (loaded a piece of PLA into a Dremel and basically drew on the helmet slowly).
After the helmet details were added, I simply strung each of the pieces together with thin elastic cord, which is got from Walmart in the craft section. One piece of cord holds the arms in place, one for the legs, and one for the helmet. You can stretch the cord as tight or loose as you like. If you leave a little left over at the ends, you can tuck it into the limbs so the joints are free of obstructions.