how GA friendly Geneva is, as far as crossing their TMA is concerned.
Notoriously unfriendly. They often have a NOTAM stating that VFR transit through the class C airspace will be systematically refused unless you are landing at Geneva. They have been criticised by the Swiss accident investigation board for not helping the pilot of a C182 who was unable to maintain VFR while transiting south of Geneva in September 2004; they repeatedly reminded him not to climb into their class C airspace, even when he said that he couldn't maintain VFR. He and his passengers died.
I'd always plan a route that didn't rely on getting a transit through the Geneva TMA. If you get a transit you'll be happy, and if you don't you won't find yourself hurriedly re-planning as you fly over the mountains.
On a much happier note, they have been known to approve low-level transits over the airport and the town centre at quiet times. This gives some fabulous views.