Sanji doesn’t fear that shit fr
The insectphobia is more of a gag
What actually freaks him out mid fight is turning into the likes of his siblings, to the point he would be happy having Zoro kill him
Okama fears are more like a low-hanging gag for Oda.
So I think he'd definitely use it.
Now Sanji's real fear is becoming and evil-no-emotions-Sanji, so of anything, I think that could be a main MMA fight for Sanji. Although, I would still love Sanji to be like "whatever fears you pull out of my head, I am still going after you" toward Killingham, and if that ends up in unlocking CoC, that would've been nice....