Making wikipedia easier to use for everybody isn't a terrible violation of basic wiki-nature, it's just being nice to users. And, that -- in my opinion -- is a just a good idea.
If "Anybody can use any skin they want!" were true, I would agree with you 100%.
But only logged-in editors can use any skin they want. Forcing editors to log in to use useful features is a violation of Wiki-nature. I'm willing to hedge on "terrible".
I'd first try to develop an interface that avoids confusion without requiring cookies, etc. That would be the optimal solution.
First, "wiki-nature" is a vague and somewhat undefined entity.
While I would certianly agree that it is valuable and could be violated, I would also argue that there is a reasonable requirement that you explain what it is in "wiki-nature" that would be violated by this proposal.
Not only that, while I agree that the "wiki-nature is valuable, I don't agree that it is an ultimate value, so I would also think it reasonable that you explain why precisely it is that convenience for users of the wikipedia is ''less valuable'' than the particular aspect of wiki nature in question.