I don't like sweet frosting and i heard you can mix 1 container of cool whip with 1 box of pudding and flavor and i could color it. My question's are
1. How would i mix this milk or just cool whip and pudding?
2. Would the icing mix hold on a cake well? (i am making a dress cake with the doll in it)
3. How long can the can sit out with this icing mix and be safe (not melt)
4. Has any one ever tried this? How does it taste???

The cool whip + pudding idea doesn't sound particularly appetizing to me. If you object to sweetness and are thinking in terms of something soft anyway, why not just use a whipped cream frosting? As in heavy cream that you whip yourself. You can add as much or as little sugar as you want. It's difficult to improve upon mother nature with artificial substitutes.

Sweetness is the whole point of frosting to me, but it's an interesting idea. Buttercream is basically butter, sugar, and a splash of milk. Boiled frosting and poured fondant essentially are sugar in an exotic form. Rolled fondant is sugar with gelatin. Cream cheese frosting is basically cream cheese, butter, and sugar. Without the sugar it would just be a kind of buttery cream cheese. If you are thinking in terms of chocolate, perhaps ganache could be made with very little sugar. Marscapone might be another possibility.

I would skip the cool whip. You can mix real whipped cream with pudding powder and get a mousse - you could likely ice with that. There is also a product out there called Rich's Cream or Bettercreme which is basically a liquid form of cool whip that you whip yourself (tastes very much the same). If you tried to spread ready made cool whip on a cake, it would break down too much.