Re: Nice idea in theory, but...
Do you really think that couldn't happen again with a civilian flight that doesn't have a head of state onboard?
I think it's reasonable to expect a charter paid for by the Swiss government, possibly with Swiss officials onboard - after all, he is asked to testify as a witness in a Swiss investigation so the expense is justified, and so is the political cover. Unlike Bolivia, Switzerland has serious EU leverage, so if the US is really so desperate that it will interfere with a proper judicial process there will be hell to pay.
If the US has not yet fully realised its precarious position in Europe it will discover it when they try to interfere with a judicial investigation by a neutral nation. I'm not sure the US can risk the opposition of the whole of Europe (which will include Russia).