Honestly I hope Blackbeard is not a AdvCOC user, and fully relies on his DF to fight. He's got more than enough AP to deal massive damage with the Gura
He perma scarred Shanks that still hurts him now, so I think he is unfortunately. Similar to Kaido and Osens and Zoros scarring of him. I even suspect Akainu may have done the same to Luffy.
As much as I want BB to get further wankby having Advc CoC, I'd prefer it to be what would counter him instead.
Make him like Kizaru in Film Z where he relied too much on his DF as Zephyr said to Kizaru and with B having 2, maybe even 3 DF, this would be extremely apt too.
Let BB and his crew rely on DFs and thus shortcuts to strength/power too much and thus haki be their undoing, to throwback to what Kaido just said about haki and DFs and how Garp, and Roger kicked ass and the latter conquered the seas with no DF, just haki and their own strength.
Shanks and his crew have avoided DFs lime Roger and his crew too, Mihawk has avoided them too and they're extremely strong and successful despite that too.
But I see Blackbeard with his truly immense and ruthless ambitions getting AdvCoC too and getting that CoC clash with Luffy too.
As you said though, I rather he just focused on his DFs and showed their full potential and awakenings, both DFs are completely insane alone, Yami has INSANE potential too especially with awakening too and god knows what the 3rd DF will be if he gets one but I'm sure it will be a god fruit funnily enough or even the literal devil/Satan fruit, sea devil of OP even? Davy Jones maybe? Will of Davy? Lmao. Davy (Jones) Back Fights...