This theory suggests that Queen the Plague’s devil fruit is a Zoan-type Scorpion fruit, and here’s why.
Just previous to the Zou arc, we see Jack and his fleet prepare to launch an attack on the marine battleships that transfer Doflamingo on his way to be imprisoned in Impel Down. Now, the front of the ships have a Mammoth head on them. Looking back on it, it makes perfect sense. Jack is a calamity and he has his own fleet of ships marked with his ability essentially.
But then, when Jack re-appears during the Zou arc, in attempt to kill Zunisha, we can see that some of his ships were replaced with Scorpion headed ships.
Perhaps as a result of his failed attempt to rescue Doflamingo, he lost some of his ships, and he was reinforced with different Calamity’s ships. Back then we already knew it could suggest another Calamity’s ability. It was a subtle detail, but one befitting of Oda’s writing and foreshadowing.
Another thing worth mentioning is that Jack’s human form appearance implies his powers heavily. The brown fur coat, and the knives that resemble tusks.
I think it would be fair to assume the other two Calamities may also have certain design choices that would imply their ability.
After taking another look at Queen’s design, his ponytail really resembles the tail of a scorpion. Another thing to associate Queen with the Scorpion Zoan fruit is his title – “Queen the Plague”.
In addition to all of that, we find out that Queen is also incharge of torturing Kid and Luffy, which makes perfect sense with the Scorpion which has poisoning abilities (infact we see Queen messing around with Kid’s arm).