I guess you have to have experienced how a pattern making program works in comparison to a CAD program to understand how wildly different they are. I dare say, as much as Blender and FreeCAD can be from each other.
I don't have anything against a fabric pattern workbench in FreeCAD, but what I don't like to see is the duplication of efforts. Already, Valentina was forked into two opposite projects because of a dispute between its developers (the other one is called Seamly2D and has retained the Valentina-project.org domain). Having a third effort with FreeCAD only divides further the efforts between very few potential contributors.
Maybe it would make more sense to create a bridge between FreeCAD and Valentina/Seamly2D, like what was done with the OpenSCAD workbench. And ensure FreeCAD takes care of what it does best, 3D.
Interesting trivia: AccuMark 3D (the 3D package from one of the main companies in the field) is powered by Blender. http://www.gerbertechnology.com/fashion ... cumark-3d/