sure, but that would mean giving Sanji the upper hand for once... (fire vs plants) when he fights GB
As GB said, you cannot hope to defeat an Admiral of the Navy by expoiting an obvious weakness and he also demonstrated counters for it (CoA, Fireproof Woods, Rebirth etc,.).
also that black blade still not addressed yet...
Pretty sure it isn't a black blade at this point, it recieved next to no attention at all lol.
Besides, Kizaru has only been paired up with Right Hand Men - Marco, Rayleigh, Beckman - and has already clashed with the former PK's right hand as he tried to kill the Future PK's right hand. Also, how he's been portrayed as Sakazuki's Right Hand Man.
All points towards Zoro vs Kizaru