Oda has slowly been building up the Blackbeard Pirates as the second coming of the Rocks Pirates but unlike Xebec, Teach will surpass him just like how Luffy will surpass Roger. Otherwise, what would be the point of alluding to the growing parallels between Teach and Rocks if it doesn't go anywhere. Oda could have just settled with Buggy then and stop wasting everyone's time. Teach told Ace, many years ago that he had a plan to take over the world, we know Teach is a reckless man, but we also know he does not make such bets unless he knows he is going to win. Plus, what would about Oda's avatar Shanks obsessing over Teach if he knew what dangers, that the World Government is capable of?
In addition, the Yami Yami No Mi. Oda has been blue balling us for decades about what this damn fruit is capable of, but one thing is for sure Teach bet his entire dream on finding this fruit because as he told Ace, if he didn't find it, he would have just given up. Knowing what we know now, are you telling me that Oda had Teach nearly waste his entire life just because he didn't know about the Gorosei, when everything indicates that Teach has insider knowledge that he should have no business knowing about? Its super obvious that whatever the Yami Yami is capable of, should be enough to defeat the Gorosei but more importantly Imu.