One of the reasons Belgium is better than Switzerland as an invasion corridor is the rail system. The rail net from Germany through Belgium to France is a lot denser than Germany through Switzerland to France, and the topography makes doing damage easier in Switzerland easier and repairing damage easier in Belgium (you can replace bridges a lot faster than tunnels or long stretches of trestle). The only way you can supply a rapid advance in 1914 is using rails, trucks are limited and roads crap and horses move too slowly. Going through Switzerland is just a bad idea. As far as threatening Italy goes, remember Italy was part of the Triple Alliance, although they bailed.