This will probably work, but two comments.
First, I think that switching back to unshuffled will still leave you with the shuffled rotation. As with many of the config settings, we might want to distinguish two instances of the rotation - the one in the config (which doesn't change on a whim) and the one used by the server (which can be copied and perhaps shuffled on server creation).
Second, it looks like the algorithm will swap *all* arena_ maps into first place, one after the other. It makes no difference for the result, but was a bit surprising.