If I've understood you correctly, the space you're interested in is *Generated*. You can take its 0-1 Z coordinate, and use some mapping of that as a factor in a Color Mix between 2 manipulations of it:

[![enter image description here][1]][1]

Below, the mapped image is mixed, 

[![enter image description here][2]][2]

but you could mix the vector-spaces directly:

[![enter image description here][3]][3]

Here, to scale the top half:

[![enter image description here][4]][4]


  [1]: https://i.sstatic.net/Xcej7.png
  [2]: https://i.sstatic.net/4KhnJ.gif
  [3]: https://i.sstatic.net/yNPRe.png
  [4]: https://i.sstatic.net/lTSBQ.gif