The height limits pretty short for a building game. So, if any one out there would like to make a plugin to raise the height limit, that would be awesome! I hear Spout has the ability to do this, not sure.
The Spoutcraft client supports any map height and you can generate it and play in SP already. Server-side support won't be integrated in Spout, but another plugin could be made to do it and the Spoutcraft client will support it automatically.