I am saying that since we cannot measure the speed of light without space we do not know if the speed is dependent on it. I believe that space something, not a vacuum in the true sense of the word, and if it is expanding it is either becoming less "dense" or more space is coming from somewhere...
we cannot measure the speed of light in a vacuum only in space, and since we are told that space is expanding it could be that the speed light varies through time.