Aha:
Turns out thats a no go and I totally forgot about that detail?
"Rectangle textures contain exactly one image; they cannot have
mipmaps. Therefore, any texture parameters that depend on LODs are irrelevant when used with rectangle textures; attempting to set these parameters to any value other than 0 will result in an error. Similarly, no mipmap filtering is allowed; GL_TEXTURE_MIN_FILTER must be GL_NEAREST or GL_LINEAR. Similarly, they cannot be used with any of the gradient or LOD texture accessing functions.
Also, wrapping modes for each coordinate must be either GL_CLAMP_TO_EDGE or GL_CLAMP_TO_BORDER."
Man miss Metal :D