We use a commitment scheme in Namecoin. There is a NAME_NEW transaction that is done first that secretly reserves the name. This transaction is then spent, a mi

We use a commitment scheme in Namecoin. There is a NAME_NEW transaction that is done first that secretly reserves the name. This transaction is then spent, a minimum of 12 blocks later with a NAME_FIRSTUPDATE which reveals the name and sets the initial data for it. It would be quite difficult to do what you suggest unless you can pull off a 51% attack on Namecoin for at least several hours, and if you can do that you probably do it to Bitcoin as well.