Seems like a fun idea.

Not for Dio, Kira, Diavolo, and Pucci tho.

Iggy does from dog issues (I don't know, I'm not a dog, I was born in a test tube to be the Jesus of Atheism)

Kakyoin either goes to Morioh with Jotaro and helps with Kira, and then die in Stone Ocean, (though Pucci probably would of had a tougher time against the 20 meter radius Emerald Splash), or Kakyoin looks in another part of the world for the source of Stand arrows (like Jotaro and Polareff did), or he just goes home, OR e goes with Polnareff to Europe and dies to Diavolo.

Advol probably stays in Egypt and stayed in contact with Joseph and end up being Old Buddies.

I think Iggy would go with Pol to Italy and would die ether around the same time Pol loses his legs or in the final fight (IMO I would have him die in the final fight.)

Kakyoin would most likely be option 1 and would help in P4 and P6 but ultimately die against Pucci but his death could maybe stall for the group and give someone like Jotaro or Jolyne enough time to kill Pucci.

Avdol would probably be in P4 and would go with Joseph to Morioh while helping the others and I could see him ether diying against Kira or surviving but returning in P5 in the place of Koichi and Avdol could be the one who looks into Giorno and die to Diavolo in Pol's place.

Iggy dips the second he can and lives out the rest of his happy dog life...

Avdol probably accompanies Joseph to work further with the Speedwagon foundation, and probably joins Joseph as one of the people protecting him when Joseph goes to Morioh...

Kakyoin stays with the Speedwagon Foundation, and probably accompanies Polnareff on his trip to meet the Boss, and since HG would give Diavolo some trouble, Polnareff and Kakyoin might make it out without a severe loss in limbs(they'd still lose though, they escape with their lives and nothing else)... this would lead to the Requiem Arrow falling into their hands, and might eventually put Diavolo into a more active position within Vento Aureo...

IMO I think Kakyoin would be with Jotaro more in the future as they had a closer relationship. I think Avdol would probably try to help Pol but wouldn't be until P5.