Why didn't the Order avoid Battle of Seven Potters fully by transforming Harry instead of others? [duplicate]

This question already has an answer here:

• In the Battle of the Seven Potters, why didn't Harry take the Polyjuice Potion? 3 answers

Battle of Seven Potters was risky. Lives were at stake and it was also a possibility that the original Harry got killed. Why didn't the Order transformed Harry using Polyjuice Potion instead of others? Harry could become an Auror, any of his friends or simply a muggle. Also, I don't think "The Trace" could be a problem with this because we have seen Harry using Polyjuice Potion when he was in second year (when the trio were spying on Malfoy).