I'm going to be real with you man, I doubt Oda just makes 3 out of 7 OG Warlords Celestial Dragons. This also really raises some rather unnecessary questions on why Crocodile just had his hand taken instead of being killed and Mihawk is not injured whatsoever.
I have in the past speculated myself if Mihawk might be in some way related to Imu/a clone of him due to the eye connection I admit, but if Crocodile AND Mihawk are both god heads banished from the holy Land I think that would just be to repetitive for Oda.
Everyone is related to CDs, not just Doflamingo
Hancock was a Slave there
Kuma apparently grew up there & his Backstory is definitely related to them, and not long ago He was also their Slave
Shanks was found in God Valley & it's strongly Hinted He could be from Figarland Family, and even if He wasn't, He definitely related
OG Emperors Trio were revealed to have been Part of Rocks Pirates who Attacked CDs in God's Valley Incident
Stelly hinted that Garp is also related to CDs somehow, same goes for Dragon who We still don't know what Motivated him to Fight them
Moria's Past is a Complete Mystery & someone from Mary Geoise ordered his Assassination
Even Buggy could be related somehow because He is inspired from Wizard of Oz (Who should end up sitting on Empty Throne)
One of Vegapunks wants to be a CD
... etc
It's not about repeating Plots, but when you write such a big Story in such a massive world & introduce hundreds of Characters, you will have to create common ground, a place that you can later on use to tie in all remaining Players so that you justify when they all meet & clash, allowing you to take out everyone who's not needed in Final Act
Instead of thinking that Warlords are revealed to be related to CDs, what if you look at it the other way around, WG created Shichibukai System not only to fight rise of piracy but also to keep certain Individuals who are related to them close
They made a Deal with Doffy, and same for Kuma, and Jinbe's Recruitment was also Political, Hancock was their Slave ... etc
And look at D. Members, They already had Garp & Saul as Marines, They then recruited BB, Law as Warlords & also tried to Recruit Ace once, so aside from Luffy & Dragon, WG is clearly keeping D. Family close to them (Nefertari Family was even revealed to be both D. & CDs)
In Crocodile's Case, He has Knight Design, He acts like CDs, his Backstory is related to another Knight-Looking Guy with same Eyes as Imu, his Interaction with Doffy was definitely some kind of Foreshadowing, He met Revos before (At least Ivankov), He learned about Arabasta Poneglyph, Pluton, He hates WG & tries to Dethrone them ... etc
He is 100% related to Mary Geoise in one way or another, maybe not a Former Godhead and simply a Guard (Who maybe was Exiled because He was in a secret relationship with a Female Celestial Dragon), but i want you to think about this:
There are 19 Families in Mary Geoise and Godheads are Leaders of each Family, Five of them are Gorosei, Nine of them are Holy Knights & finally there is Imu who sits on Empty Throne, so that leaves us with Four Missing Godheads, and i can't think of any Knight-Looking Characters who could have been Godheads aside from Crocodile & Mihawk