I think your wife is quite right, I think the shirt collar needs to be open and worn outside the present sweater. A Tattersall shirt would be perfect. With the V neck sweater a tie would be the way to go.Plain brogues( not Ghillie brogues)in this case might be better , well polished, with kilt hose pulled up and flashes if you want them. If you want you have no need of a belt as,I assume, you will be wearing your sweater over the kilt, but you may feel happier with the extra security of a belt. Yes a plain sporran.