prefacing this entire post with "in my opinion":

I'm relatively new to thinking about formal kilt wear but that is a gorgeous coat. From a practicality/wearing it stand point; the full vest is a must, not the low cut that is common with say a PC. It will emphasize a fit build. Having the wing tab collar is a given but have you considered wearing a silk cravat tied with a loose 4-in-hand knot? That could give it modern look while retaining the classic formality that is depicted.