The part wouldn't happen because he would have killed Diavolo first encounter.

I disagree. He would've lost his legs, yes. But, somewhere along the run, he would've met Kochi (or say, heard him muttering Jotaro's name), asked shim about Jotaro to which he would come to learn of Polnareff's situation and boom Josuke gets involved. (Considering JoJo logic, I 100% believe this to be possible)

Do you Mean Josuke? who does Jostle mean?

FUCKING AUTOCORRECT BRO

Though I feel like josuke would just get oofed by KC or just save Abbachio, (Copuimum wanting to save my fave gucci goth from, becoming a grape donut.)

You see, I have a theory abt this continuing tbh. Once Jotaro meets Polnareff again and gets Josuke, I believe Okuyasu would automatically want to get involved which means two new party members. However, he wouldn't die. I think, he, Okuyasu and Koichi would've been together and scout elsewhere when they would come across (Okuyasu to be specific) Abbacchio DYING as they went to check on him. Josuke is obv quick to save him as he is literally SECONDS away from dying, to which they then spot you know who

Edit: Or JoJo's Marc Spector would already be long gone.

Its also possible for Doppio to kill Josuke instead yl off one of the healers, since hes smart enough for that

That is true, but keep in mind, Doppio immediately bolted when he went in for the kill. It is unlikely for him to go back to kill Josuke (unless we're talking about the next time they meet which is then a possibility). The time where Doppio killed Leone was also the first time he ever got close to Bucci's squad so (unless my memory serves me wrong, not counting when he killed Bucciarati btw)