I think your proposal is interesting, but it's going to be a lot more effective to find cars and car-sized objects, than to find individuals.

It's very difficult to find individuals on the ground when you're searching by air, by the way, unless they're very aggressively trying to be visible (by using a signal mirror, for example). You just can't reliably spot something human-sized from the air, because of the speeds and distances involved. You're moving at a minimum of 75 mph or so (even in a helicopter; they can go slower or even hover, but that takes a lot of power, and burns fuel at a truly amazing rate), and are typically at least 1/4 mile or so away from the target (probably more).

Something car-sized is about the smallest thing that an air search crew can fairly reliably spot during an air search. Even that depends on a variety of factors, though; a silver car, against a snowy backdrop, partially obscured by trees, is going to be a real challenge to spot from the air.

I'm not sure what the resolution would be for the aerial or satellite photos that you're contemplating, whether they'd be sharp enough to make out an individual. Finding a missing car (or, in the case of a missing aircraft search, the crash site) is very useful, though, and can get you a lot closer to finding the individuals you're actually seeking.