Dragon wouldn't make much sense, they simply can say that it's him, the revolutionary dude.
Though I though the same about Aokiji as not being the 10th titanic captain, and Oda retconned blatantly lmao, so it might be a legit option here as well.
Saul for sure doesn't fit anymore.
New character fits better, and I like that idea about Davy Jones. Though, wasn't that the name of Vander Decken ancestor? Or was smth similar I think.
Regardless, a new character, yes.