Actually it appears from spoiler that Queen is targetting ONE SPECIFIC Flying 6 member, meaning it feels like he wants someone in specific who's been a headache for him (My assumption is Who's who, because he's threatening their positions)... all in all, I think this is a good way to showcase that Calamities cannot slack off because of F6 waiting for that seat, and F6 cannot slack off because maybe a headliner can get stronger and accomplishes something noteworthy to challenge those F6 and take a seat.... it only speaks about the strength of Calamities/F6 honestly. and it never points to the idea that anyone can fill the position.... And I repeat, the feat is taking out Zoro and Luffy... Queen is not stupid to not know that these guys are heavyweights... even if he called Luffy with some names in Udon prisons... he called BM with some names, so it's not really important