We will hike from Chamonix to Zermatt finishing on September 3. We have four nights to play with at that point. We have yet to book the return flight. Thinking to spend 2 nights in Zermatt and then maybe go to Bern for two nights to experience a different aspect of Switzerland. Fly home to Seattle from Zurich or Basel. We aren’t really big city people so don’t want to stay in Zürich. Thinking Lugano is too far for the short time? Would love to hear your thoughts!
Bern is a delight and it's a 70 minute trip to the Zurich airport by rail, so I think it's a fine choice.
Bern is worth a day. Luzern is Alps, and on a lake so different to Zermatt and Chamonix.
The only transatlantic flights from Basel are to Montréal. If you want a direct flight you will need to fly from Zürich.