im a building engineer/analyst working at Atkins, we have done various research on elevated retail/what you have said - and frankly speaking it does not work. you need a huge core to carry all the logistic upwards to the sky retail. no issue here but the thing is most developer will not agree to part ways with huge GFA considering this core can take up 64m2 per floor plate, imagine if the building is 25 storey high to reach the retail area, thats 1600sqm of nett sellable space. 17000sqft x wtv is your selling price (assuming 1k RM) = 17 mil.

there you go