As the lady of a man with a kilt, I have to say, I'm not entirely sure why your wife is objecting. Frankly, I'm trying to convince my man to wear his kilts more often.

I would suggest that you ask her to just let you wear it a couple days and for her to watch the people around you. Dress it up smartly, casually, whatever way feels best. Regardless, there's nothing quite like a man in a kilt and if you're lucky (I cross my fingers for you) she'll come to realize that. Best of luck to you!