A lot of DAZ assets are not ready for iClone physics.
Depending on the UV, materials may just need to be consolidated into one and then probably re-textured,
or if the UV maps for materials are overlapping, then new UV unwrap would also require.
So for your case, again, if the Hem and Front_Back are using the same texture maps (even though for different parts),
you may safely consolidate those in iClone and then make a gradient in Blender.
I strongly recommend Blender or other 3D apps (3DCoat, Substance Painter.. etc) because looking a the UV unwrap through Base Color,
I'd say it would be hard to match front and back with the same gradient in 2D painter.
Even a small inconsistency might result in deformation at the dress sides where unwrapped mesh is connected... not to mention the Hem.