I like where your brain goes but have a problem with the plot holes. Why not just send the look alike in the first place? And what happens to the fishing buddy? Is he in on it too because I think he would recognize the switcheroo - especially on the 9 hour drive back to TX. So now there are 3 people involved in a conspiracy to lie to LE and provide an alibi for someone in a murder investigation? Nah. I think this is a little far fetched. You know the old saying, 'two people can keep a secret if one of them is dead"? It is true. But, I like knowing that it is possible to disembark and go retrieve a cell phone at the counter.
Bad weather can't be planned ahead of time so this would make the plan even more challenging and In every experience with bad weather and departures that I have encountered, you board the plane and it backs away from the gate and everybody sits there, waiting for the weather to clear. The airlines mark it as an official on time departure because it left the gate. No one gets to get off and go lolligag in the airport awaiting a call that they can board again. It is like captivity. Ever de-ice for 5 hours at O'Hare?
Plus, the flight attendants have the manifest of all passenger names and assigned seats. Missing passengers are noted, searched for briefly and their absence is logged on the manifest and reported to the pilot and the gate attendants. They know who didn't get on the plane.
Let's assume that all the agencies involved in this investigation know how to corroborate an alibi through independent sources. I mean, they are the pros at this afterall.