I am just going through some of Caulaincourt's writings on the situation in June 1815. Napoleon was just abdicating and the provisional government was wondering who could replace him. They feared the Bourbons. Some thought the Duke of Orleans would do. Nobody took Napoleon II very seriously. But, and I had not heard this before, some other names were mentioned as possible candidates for the French throne during the course of one of their meetings. Caulaincourt says they were the Prince of Orange, one of the young grand dukes of Russia and, a bit of a surprise, the King of Saxony. They preferred the latter because he was Catholic.
He says this discussion was never made public. It is certainly the first time I have seen it. Events overtook it pretty rapidly.