Alright I have a new idea however, I am not sure how this could be implemented in GLScene.

To start off here is a better definition of what I am looking for: To be able to blend tiled (repeated X and Y) textures over a mesh (a terrain).
The effect would give the ability to "Paint" a texture in my level editor.

Now the Idea I have to make this look how I want it:
Somehow to apply the texture over the whole surface and then apply the blend_mask on each tiled texture over the surface.

So for each material (texture) i have in the MaterialLibrary I will need to have Non tiled Blend Mask.
Then somehow apply the mask over the tiled texture that it is linked to. Then to do this for all of the textures in Library.

I have a feeling I might be going about this all wrong, because its starting to make my head hurt thinking about it.