If the colors and tones of tie and shirt are more subtle and really look better in person, go for it. A waistcoat might be nice as an option, but I don't think you need a waistcoat with a kilt. Actually, I don't think I would wear that shirt with a vest; you wouldn't see enough of the pattern. I would use a different pocket square; try a color from your tie, maybe the violet. Good luck with the sleeves; I would discuss what you want with the tailor before leaving!