As mentioned above, i agree it wasn't his main goal. He wanted to be acknowledged, but to do that, he indirectly wanted to do better than his dad and thus aimed for the one piece
He either wants WB or Luffy to become the PK. So he could be their first mate in the end as the best scenario, unless you need to kill both. WB was old and he wasn't going to live more, but Luffy was young and he wasn't going to die, so that wasn't going to happen without Luffy dying.