Never cooked/done couscous so don't know what's involved with it. I will find out though.
Couscous is a great vehicle for other foods but I wouldn't use it with stir fry and certainly not for your guests without experimenting first.
It has many uses and is a great substitute, in the right situation, for rice, pasta etc. It works extremely well with Moroccan food and foods from that general area.
As couscous has no flavour it's what you add that creates the dish. A favourite of ours is a chilled couscous salad, basically very finely diced veg mixed with couscous, oil and vinegar alongside oven baked salmon.