I want to star by saying I love this game and that, though I am about to offer a small critique, it does nothing to take away from the game. Honestly it really doesn't matter and is just me being a bit nit picky, but it could matter to someone in real life.
All this build up to say that a great kilt is not formal dresswear. I know that may sound weird to some people, but a great kilt is more workwear meant to be functional and protect you from the elements.
A formal kilt is called a dress kilt. It is made up of, the dress kilt itself, a dress shirt, a formal jacket (there are several styles), a fly plaid and brooch, dress hoes, a dress sporran, flashes, a kilt belt, a tie or bowtie, and ghillie brogues aka kilt shoes.
Again none of this really matters in the game, and honestly would probably be a pain to implement, but in real life if you show up to a formal Scottish event in a great kilt you will not be let in. Anyways rant done and once again I love this game and I am not asking this to be changed in game.