First, I certainly don’t think you are “crazy.” However, personally I wouldn’t do it unless it was the red eye on the way home. Flight time is maybe 30 mins longer, plus an hour connection plus and hour back to las. For me, not worth losing at least 2.5 hrs each way in Vegas. You are basically adding 50% (or more if something goes wrong) to the travel time. Can you just take the jfk-las flight with flatbeds?