It is easier to guess which 6.0 skaters could have navigated IJS as successfully as they did 6.0 and which perhaps could not. Kwan would have suffered some under IJS because of her spins.
It's harder to judge how skaters under IJS, like Kim Yu-Na and Mao, would perform under 6.0 criteria. You have to take the imaginative leap and consider how their style and performance would be different--and most likely improved. Under 6.0, Kostner would not be world champion-- not unless they brought back figures.