This is only about the Schengen, Switzerland is not a part of the EU, and even before the Schengen, the borders between the EU and Switzerland weren't heavily controlled. I got in trouble at German airport for going by train from Lausanne to Milan, and then plane to Berlin, I had no entry step into the Schengen because they didn't bother doing that on trains (pre-Schengen).
Everything else is negotiated under separate treaties. This would revert Switzerland to pre-Schengen, which is sad, but it wouldn't be suicidal.
Everything else is negotiated under separate treaties. This would revert Switzerland to pre-Schengen, which is sad, but it wouldn't be suicidal.