Well it's not a Greenhill's Cube, but I have not seen it done before.
I have made a Pocket Missing Link and an Extended Missing Link before so I took it one more level this time.
Here is my Mini and Mega Missing Links.
G-Mixed_Links.jpg [ 17.24 KiB | Viewed 524 times ]
On the Mega Link, instead of having all 4 middle sections fixed, I decided to do 2 and 2. Here is how the middle sections move.
I also made a staircase cube
C-Stairway_2x2x2.jpg [ 21.9 KiB | Viewed 524 times ]