I quickly tested the feasibility of it, and it doesn’t seem to work.
Transmutr creates V-Ray 3.6 materials (because we want to support back to that version). When you open a transmuted file with V-Ray 4, the material data is updated by V-Ray.
For some reason, when I enable the Texture Mode in the material, V-Ray disables it when updating the material to V-Ray 4.
So it looks like it’s not possible, sorry.