I second this option. Flying into GVA would put you a bit off center, depending on what places you want to explore. Flying into ZRH and I would pick either ZRH, Bern or Luzern as a base, as central as possible or as easy as possible when it comes to train connections to the locations you want to visit. I would think Bern or Luzern would be the easiest as they have lots of access to various resorts and mountain touristy towns.