He's a martial artist and seemed like the most important underling along with Shiryu. But yeah, there was never a strong argument.
GB, I can only see him as Sanji or Jinbe's opponent. Kizaru and Fuji both make way more sense as Zoro's opponent. Plus GB's weak to fire so Sanji's well suited to fight him.
Same here, I don't see there is any way that does not include a massive retcon that will ever give EoS Lanji the stats to beat a top tier. GB is thus the only top tier he can beat due to elemental advantage, so Lanji vs GB makes much more sense than Lanji vs Kizaru.
The thing is, for me Zoro vs Kizaru and Zoro vs Fujitora are both a win-win scenario. Zoro vs Kizaru's appeal is obvious, whereas Zoro vs Fujitora means Zoro's gonna beat the only OP character with interstellar-level feats and a likely future FA. I'm fine with either way happening, although at this point of the story, Fujitora seems to be Sabo's opponent more than Zoro's.