Hi,
skyguide training is done at Dubendorf near Zurich. They pay a minimum salary during training which you would need to supplement from your own reserves.Posting after training is up to the company and you could be posted to any location. skyguide do not always take language skills into account when posting as in the past they have posted non french speakers to geneva and non german speakers to zurich. There is also Bern and Lugano as possible posting locations. The only sectors that have french published as a control language are geneva approach & tower. Elsewhere the published controlling and training language is English. Their training success rate, beginning to end was about 50%. Some foreign controllers have failed to check out in some units. Local politics especially in the geneva area can get personal (they like you or they don't). Their training school in dubendorf used to be very good, but then a wave of instructors resigned due differences of opinion with the school management. Overall skyguide work conditions are good and the salary also good after training is passed. Tax in switzerland changes with location, but depending upon your situation & where you live will be between 17 and 25% after deductions etc.
Make contact with them and see what they tell you then decide for yourself.