I have given some thought to using a system similar to your idea for just the engine. By essentially "tenting" the engine area with a not-especially-tight seal around the cowl and where the tent meets the hangar floor, and then pumping enough dehumidified air into the tent to extract the moisture from every crevice of the engine. For the engine, this avoids reconditioning crystals, hooking things up to intake, exhaust, oil filler, etc. Similar to dehumidifying the hangar, but requires much less volume of dehumidified air. No reason it wouldn't work for other parts of the airplane. In fact, your idea might be easier to implement because the volumes you are proposing to dehumidify are already somewhat air tight. Maybe instead of blowing in one orifice (like the storm window) and drawing out air from another, you could just blow dehumidified air in, and let the moisture-laden air leak out of all the small exit points.