This sounds good in theory, but I'm not very tall(5'-9"). So if I had a really tall ladder, I would need another ladder just to reach the higher level of the main ladder, which then would not be BIAB on the cheap -- these ladders are expensive!!!
And if I remember my physics correctly, the further from each other 2 objects are, the less gravitational attraction there is. So a taller ladder would actually reduce the pull of gravity on the bag. Probably by a good one ten trillionth of a percentage point. No thank you. Couldn't afford that drop in efficiency.