Honestly, after rereading the recent chapter, I think it’s more likely that Bonney will join then Vegapunk. (If one of them join for raftel)
1. Inherited Dreams are a big thing with the straw hats. As such, I believe that Kuma had a dream that aligned with Vegapunk which is why they turned Kuma into PX0.
2. Vegapunks dream is definitely a major dream; however, I feel Vegapunks character just doesn’t mesh with the straw hats. All the straw hats have someone close to them who’s will is connected to their dream. Vegapunk seems like he is connected to Clovis but then it kinda rips into robins inspiration.
3. This is where Bonney seems to fit. If kuma shares a dream that aligns with Vegapunks that Bonney would inherit from her father who died attempting to complete this dream, it’s definitely a straw hat type backstory.
But I may just be bias cause Vegapunks been kinda a let down.
My current preferred list of people to sail with the straw hats in this arc:
1. Shaka - I like his style but he’s likely to die
2. Bonney - I like her personality and backstory
3. Lillith - May be a bit evil but she at least has an entertaining personality.