Update

Fix for extensions packaging: Work in progress
Thanks to Davide Punzo for working on Units support
Use SimpleITK's Superbuild in Slicers Superbuild?
- https://github.com/Slicer/Slicer/pull/308

To Discuss

There are no problem to have superbuid of superbuild. Jc will integrate SimpleITK request as soon as packaging issues are addressed. Few considerations:
- path should remain short to avoid path length issue on windows