Connecting via EWR will give you Polaris SFO-EWR and enough time for the Polaris lounge in EWR. SFO-IAD would be regular first class (regardless of widebody).

I'd avoid LHR since there will be border control on the Eurostar (and at LHR). Plus having to go from LHR into London to catch the Eurostar... GVA airport is a short hop to the main train station.

Net it all out, I'd go SFO-IAD-GVA. I mean, once you're in Geneva, you're pretty much in France...

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