There are some wonderful routes in Switzerland, using mountain hotels (Berghotels) and Alpine Club huts. For a 4-day trek, you could start in Lauterbrunnen and walk up the upper valley to Obersteinberg, where there is a very rustic mountain inn (no electricity). From there, climb the path up past Gimmelwald into the Sefinental and spend the night at Rotstockhütte. Next day cross the Sefinenfurka (pass) into the Kiental and then up to a high pass (Höhtürli) where you will find a stone hut, Blümlisalphütte.. (There could be snow here in September, in which case you might want to skip the high pass and take Postbus and train to your next destination. From the high pass, you drop down to Oeschinensee and another mountain hotel where you can stop for the night or just have a late lunch before continuing down to Kandersteg, where you will find train connections.
This is a section of the Alpine Pass Route, and there are others you could do instead, such as from Engelberg to Grindelwald. There is a guidebook by that name which would be a good investment if you are interested in hiking part of the route.
Another possibility would be 3 or 4 days on the hut and mountain hotel circuit in the mountains above Zermatt:
http://www.zermatt.ch/e/hiking_trails/map.html