Very well, as you wish.
Just saying right now that if it will be "undercover mission" (deployment), "during night" (shade) in "polar environment" (terrain), you will NOT be able to use only "undercover weapons only" (deployment), "night-capable weapons only" (shade) and "weapons working in polar environment only" (terrain). You will only be able to choose one of these conditions.
Also, when you start categorizing weapons... let's make an easy example (category 1: ranged, category 2: melee, category 3: grenades), you will NOT be able to create a mission where you can use category 1+2 weapons. You will only be able to choose 1 category. If you would like to use weapons of category 1 and 2... you will need to create another category 4 and do all the work again. If I was modding, that alone would probably totally discourage me from using the feature.
It will work perfectly fine for your custom "undercover mission", but as soon as you will try to create another custom mission, you will start having problems. With each new type, more and more problems.