Is FengGUI capable of being rendered on an object insode a 3D scene? I think, this is what he wants to achive.
There is no way to render FengGUI widgets on textures (efficiently) yet. But since they are rendered in the "normal" 3D space, there is no argument against modifying the projection and model matrix a bit.
I toyed around with the a bit couple of months ago and it worked quite well. It is a bit tricky though and I havent materialized an official example how to do that yet. We will probably come up with an example as soon as we have our little "effect framework" in place.