It is just a idea for a shape mod that I didn't manage to build, in case someone else finds it interesting.

The idea is to obtain two fused cubes like them:



It could be modded from a rubik's cheese, where each of the pieces of the cheese corresponds to an edge of a cube, and the central plane of the cheese is the line in red here:




OK, photos aren't good but the idea is easy
(Of course these pictures are from a cast puzzle, not a twisty one)

Some has but it is in a cube version.

http://twistypuzzles.com/cgi-bin/puzzle.cgi?pkey=3596