I frequently add turtlenecks under my sweaters and I think it looks very sharp - just as long as everything still coordinates.

However, I've never liked the look of a shirt & tie under a standard sweater. Too much is hidden. If you really must wear a shirt & tie then my suggestion is go for a V-Neck sweater. However, since it is going to be with a kilt, not an Argyle V-Neck.