What is not possible is to have a false unification that means that we point es.wikipedia.org at a different organization with no guarantee that they will do things in the wikipedia way.
But what guarantee do you have that e.g. the German Wikipedia is "doing things the wikipedia way"? And what would you do if you knew we aren't?
I think it's very important that the people (often just one or two) working on a new international Wikipedia are already indoctrinated with our ideals (or have a social Wp-habitus, if that sounds nicer ;-). Otherwise a new Wikipedia could become totaly tendentious, and it would be very unattractive for others to participate. I fear this will happen in the future, but hopefully enough multilingual "old hands" will allways keep an eye on upcoming Wikipedias.
Kurt