Preserving texture coordinates through mesh reductions and remeshing is not really ShapeDiver specific, I suggest you ask the question directly in the Grasshopper section or even the Rhino section: did you try to do mesh reduction and quad remeshing directly in Rhino and see how it affects the texture coordinates?
Did you find a solution for this? I am trying to achieve the inverse. So I want to Remesh with higher density but keep to custom texture mapping as cloes as possible. Any ideas how to approach this?