Switzerland has been a polyglot constitutional federal republic since 1291.
True, Switzerland can do it. It is the true version of what a Federal Nation can be. Each Canton is relatively sovereign and self-governing with very little Federal oversight. There are German, French and Italian speaking Cantons with long established histories. They banded together to have enough strength to stand up to European powers so as to maintain their independence. However, if the German speaking Canton of Zurich were to slowly find itself in a position of having 25% of its votes cast by Muslims, then I think they would have a major problem.