Imo World of One Piece have Two Scenarios, Two Sides of it
One where Blackbeard is Victorious which is Current Scenario
Luffy must turn World "Upside Down" to switch to other Scenario where He wins instead
So imo both BB Pirates & SH Pirates represent Roger Pirates
While Rocks Pirates are presented by their Greatest Rivals
In other words, in Scenario where BB Wins, He is Roger of this Era & Shanks is his Xebec
While Koby is Marine Hero who gained Fame thanks to Blackbeard's Conflict
And in Fixed Scenario, Luffy is New Roger instead, while Cross Guild are his Rocks
With Smoker being his Garp who gained Fame in Arabasta thanks to Luffy's Actions
One Piece means Two Sides of Same Coin
So for Everything, there are Two Answers with "Same Fate" but "Opposite Reasons"
Just like Fisher Tiger & Otohime for example
When it comes to Rocks Pirates, as i said, They can either be Red-Hair Pirates or They can be Cross Guild
Both will Share Same Fate, but Opposite Reasons
Even if the Characters are completely different than each other, this still applies
Sanji & Big Mom are a Prime Example
Both Abandoned by their Families, but Sanji was cuz He was "Too Weak", while Big Mom for being "Too Strong". Both Lost their Mother Figure, but Sora Died cuz She Opposed turning Innocent Children into Cold Hearted Assassins, while Carmel Died cuz She Supported the Idea. Both met & bonded with a Pirate Chef who technically raised them, but Streusen was cuz of Big Mom's Inability to hold her Hunger, while Sanji the opposite, and i can go on & on, actually every SH have a Character who represents their "Other Side of The Coin", and this applies to every single Island, Event, Arc, Character ... etc even the World itself is Split in Half
I'm explaining all this just so that Fans don't always Pick a Single Answer when trying to discover who Parallels who & who Replaces who, there are always "Two" Answers. Currently Luffy is Living in the "Bad" Scenario, the "Bad" Dream, and who's the Dreamer? Obviously the Guy who Never Slept