Your challenge, should you choose to accept it, is to have Switzerland go to war with a country that is not Nazi, fascist or communist by the present day with a POD no earlier than 1850.
The Prussians decide on a "Großdeutschland" approach in the 1860s and declare not only Austria but the German-speaking regions of Switzerland to rightfully belong to the Empire. They invade to enforce the decision. Switzerland resists.
It's not very likely, but in the 1920's or 30's the state of Voralberg in Austria voted to join Switzerland (Austria was still a republic at the time wasn't it?). IOTL Switzerland refused because the allies didn't want it to happen as well as the french and italian minorities within Switzerland refusing to add more germans to the majority. If the allies let it go through and some decent concessions are given to the minorities and its possible to go through with it. Have Austria refuse and you might get a war to enforce the decision made by popular sovereignity. Unlikely, but I think it's not totally ASB. Only problem is I can't think of a clear enough POD to make the allies so indifferent, or the swiss willing enough to fight for voralberg as even the germans of the nation weren't really overly concerned.
On a less serious note, let them invade Lichtenstein to remove the last semblance of Hapsburg power.