I just think that each Titanic Captain having an Island as their Fight Location is enough great hype for their Abilities,
I don't think they represent Top Duelists, nor do They have "Great Power" DFs except Kuzan,
However, They showcase the Threat of DFs and how simple powers can threaten even the mightiest of nations & armies,
I even expect us to have DF Origin/Lore when They are fighting,
I get your point.
How I see it is, BB represents the unchecked hunger for power. That's why he's the only person in the entire series to be able to consume more than one DF. Post-ts, the BBPs have been shown to hunt down interesting DFs. They may not be the ultimate DFs in their categories, but they're DFs that BB deems necessary for his goal, just like he said with Boa.
They might not get what they want exactly, but they will get the closest best thing.
But the DF alone isn't enough. Not for a top-tier crew. Not for a wannabe PK or King of the World. Orochi showed that: unless you have haki, you're an easy target for competent fighters.
So, do the BBPs all need to be exceptional duelists?
No. They can threaten entire nations with hax DFs.
But they do need a little bit of haki to counter other hax DFs that might try to oppose them.
I also believe that possibly Oda could give all SHs a DF,
4 out of 10 already have DFs, while Nami & Usopp fight with Living Weapons and They already buffed them with so many Techs, so why not a DF Next, and Franky can also feed one of his Weapons or Tanks or Shogun or Thousand Sunny a DF,
This only leaves us with Zoro, Sanji & Jinbe,
Sanji already told us that He doesn't mind eating a DF, and if He really does Unlock Adv. CoC, then it would make sense that He eats a DF next, cuz He is a "Super" Human, making him fall in category of DF Users who have Adv. CoC (WB, Big Mom, Loki, Sengoku, Luffy ... etc are all Near-Unkillable Tanks with Adv. CoC, unlike the Peak "Normal" Humans such as Roger, Oden, Garp, Gaban ... etc)
Not sure about Jinbe, but Oda already inserted in our minds the idea of a DF User Jinbe through S-Shark, so it's still a possibility.
That leaves us only with Zoro who might remain DF-Less, but Oda can still give him some kind of DF-User Pet like Onimaru, only to accompany him, not help in Duels.
As for the SHs, I firmly believe that none of the current members will get a DF in the future for themselves. Usopp might feed a DF to his slingshot; maybe Zoro himself to one of his swords, though I
highly doubt it.
But Sanji is an enhanced human already. He got the ability he wanted through the Raid Suit, and there will hardly be a future DF that can make him more powerful than aCoC alone can.
Also, if Judge wanted to turn his kids into perfect living weapons, why has he never fed any of them a DF?
IMO, the Lineage Factor engineering he did on them prevents them from eating a DF. Judge's tinkering affects the same part of a person's genetic makeup that a DF alters upon consumption. That's why Reiju can showcase a lite version of Magellan's DF. The Vinsmoke kids were already given a different Green Blood-like serum before they were even born, so eating a DF for them would be like eating a
second one: impossible.
The M3 are all superhumans.
Luffy is a monster who combines DF and will power
Zoro is a monster who combines swords and will power
Sanji is a monster who combines an artificial body and will power/passions
Just how I don't see Luffy or Sanji ever use a sword seriously, I also don't see Zoro or Sanji use DFs.
Franky should improve himself through scientific weaponry, even better if of his own design and not hand-me-downs from VP. Sure, DF are a scientific creation too, but I'd rather he stayed a cyborg with implants than another paramecia user.
As for Jimbei, not only do I think he will never get close to a DF, but the "fishman who has a DF ability" idea touched on in FMI with Vander Decker I believe will be used to set up Davy Jones' condition, not to foreshadow Jimbei himself getting an ability.