Paris and Switzerland
 

I am thinking it is more time and cost-effective to travel from Paris to Switzerland (perhaps Lucerne) and back by train rather than open jaw flight out of Switzerland? How about if we include Lugano in our itinerary? Thank you for any info you can give.

>>I am thinking it is more time and cost-effective to travel from Paris to Switzerland (perhaps Lucerne) and back by train rather than open jaw flight out of Switzerland?<<

Typically -- when you factor in the extra cost/hassle of returning to Paris to catch your flight, open jaw will cost less

Zürich would be the only city with direct flights to other continents.

Do you want to settle for guesses and generalities instead of actual prices and actual travel times?
In case you are not aware, you can look up train prices and schedules online at www.voyages-sncf.com or www.sbb.ch.

You can also look up actual open-jaw prices using any of your favorite online flight booking engines.

EG, CH to your home airport on skyscanner.com

If Lugano is your last stay in Switzerland, you may also consider to fly home from Milan Malpensa airport (direct buses from Lugano to MXP).
As said above, Geneva has only direct flights to Europe and the Mediterranean, the Middle East, Peking, Montreal, Washington and New York.

Thank you all for your valuable inputs. I am considering them.
neckervd, maybe we can start at Milan and include Como and Venice. Is it easy to go to Lugano then Wengen from Como? Or if Lugano and Como are similar, we can skip Lugano. End in Paris. Thank you for your help.

Como - Lugano is about half an hour by train. Trains are frequent.
Lugano - Wengen by train: 5 1/2 hrs journey, trains at least every hr, via Lucerne, Zurich or Domodossola (most scenic itinerary).