The Gorilla does have a serious personality which makes it more perfect for slap-stick and character based stuff, especially knowing the fact that he is a gorilla with lazer eyes. Trying to be a stand-up citizen of society, while being a talking gorilla, getting peeved when he loses his box of receipts and frantically searches for them.
Well that's what the voodoo magic is for, going typical gorilla size, so he isn't always a giant gorilla, rude to work with people when you are giant. 

But I can see your points. Well, except for the the fact that he is too silly for Kill La Kill! 

I have to disagree! An Absurdly Powerful Student Council, which essentially is a nation state, who have leaders powered by magical clothing that is rather revealing, and a military faction of naked dudes who fight them off!? Sentient Gorilla would fit in pretty well, probably body-guarding for Kaneo, money easily buys Sentient Gorillas.