Oda probably always planned for WW to fight Jinbei, I think also would have planned for him to reveal the Sun God slave story since that ties with Jinbei and Fisher Tiger.
The Gomu Gomu fruit thing, in the ither hand, definitely seems like he threw it in at the last minute. Probably something along the lines of him having two ideas
He was going to make this reveal that Luffy’s fruit was more important than first thought, but hadn’t made up his mind when he would reveal
He wanted WW to be an ex prisoner
And he thought “aha, I‘ll jam these plots together” and the result has been… messy
The Gomu Gomu fruit thing, in the ither hand, definitely seems like he threw it in at the last minute. Probably something along the lines of him having two ideas
He was going to make this reveal that Luffy’s fruit was more important than first thought, but hadn’t made up his mind when he would reveal
He wanted WW to be an ex prisoner
And he thought “aha, I‘ll jam these plots together” and the result has been… messy