It is precisely because Oda gives a fuck that Kidd and Law cannot be Empires. They are strong, "Great Pirates", but they do not have empires and thus cannot be Emperors.
For BlackBeard:
For Luffy:
Oda had already said Luffy would become an Emperor level pirate immediately after Dressrosa, without even Hakis and Awakenings and what have you. The second he left Dressrosa, he was there:
Remember the power of an Emperor?
As strong as Kidd and Law are, is there any remote chance of other crew being able to pull off a "you won't even get to see them?" Do they hold territory? Do they have a fleet?