I may be missunderstanding part of what you say. Sometimes the technical material can get in the way of us understanding the big picture. I would emphasise the statement in the classics that all Qi is one. We give it different names but there is not a substance called Wei and a substance called Ying. There is Qi existing in different places and doing different things, the statement 'no relate(ion) of Ying Qi to insomnia' is to get caught up in the technical material as if it was describing physical substances that could be separated (reductionism). The Dao De Jing says that we take things apart in order to understand, but then we have broken it.
The Chinese characters Ying and Wei are usually referred to as nutritive and defensive. The characters refer to the soldiers and the encampment. Defense may not be the best characteristic to focus on for Wei. I like the terms used by Porkert for Yin and Yang - 'structive' and 'active'. The soldiers are the active and the encampment is the structive. The metaphor has a flaw - one can remove soldiers from a camp. But one cannot separate the structive and active aspects of Qi. We can only describe where one or other aspects seems to predominate.