An alternative not on your list: immigrants aspiring towards assimilation into a single culture to which they give their allegiance, superseding their original one, of which nothing remains but the dressing-up aspects.

In a different subthread*, the line of reasoning went that this does not positively "deal with" multiculturalism, but rather eliminates or prevents it. This seems to be part of what is happening in Japan; IIRC they deliberately filter immigrants for willingness to blend in, though they do so in more politically-correct terms.

* This one, though most of the replies that are most relevant will probably be hidden, since it appears Peterdjones is being heavily downvoted on this topic for some reason.