>>9760515So, this is one idea. But as a toy, this has some significant problems
the blades split vertically, and each arm has 3 hinges (one at the base of the rotor, then one at the top of the rotor, then one at the end of the blade). That's 18 hinges for the arms alone. The rest of the toy would have to have really simple engineering for it to work in a price point. This probably means molded in hands, no wrist rotation, no ankle tilts, no toe articulation, no waist swivel, and maybe even no head swivel.
But it does have the advantage of being able to stay with 3, shorter legs for robot mode (you just don't move the rotor up, and that means you can't split the blades) and spinning is still easy, since it rotates at the base, not the point where the blades meet the rotor.
You could stick with something similar, but with less joints by removing the part of the blade that flips out. Then each leg would just be 2 segments, but it would mean 12 hinges instead of 18. You could also just mold the rotor/blade connection instead of making it a hinge, so it's always stuck at a 90 degree angle. That could get you down to only a hinge at the very bottom of the rotor.
A completely different direction to go would be to make the extra 3 spiderlegs actually pop up out of the tailfin in a completely different transformation.