Two Platonic solids are the cube and octahedron. These are dual to one another. For each corner of one, there is a corresponding face in the other. Keep cutting the corners from one and you get the other.
Like the hexagonal projection of the cube, the hexagonal projection of the octahedron has a bistable convex/concave perception. But this is harder for us to see since we're in the habit of living in rectangular faced polyhedra.
Earlier you had mentioned the cuboctahedron, rather than the truncated octahedron, could be a bridge between my octet toy and Legos. My first thought was "truncated octahedrons stack to fill space but cuboctahedrons don't".
Then it occurred to me cuboctahedrons alternating with octahedrons stack to fill space. And the octahedron is one of the two species of bricks in my octet toy.
The cuboctahedron alternating with octahedrons would be a very nice bridge between cubic and octet lattice structures.
Now I know of two possible ways to splice my toy onto the Lego universe.