He's not just 'one' of their top guys, he's the strongest of his generation, and actually more of a monster than they even realised at the point when he gained that title prior to the competition with Team 6, that's why they wanted to challenge him, because their Ace wanted to prove he was actually better. Yet, at that point, they hadn't discovered how he could almost instantly learn the Six Arts of Capture.
Also it might be grounds to remove him but the only people who know are supportive of it (Aoi's current main bodyguard, the ex-squad-one guy, Yodaka's own operator, and the Squad Six ace Hayabusa.)
It's also potentially a reason to not remove him because it means he will go absolutely above and beyond to protect her, which is what they want.