Actually, I was going to explain in Mercy's OC post about the battle suit. Looks aren't always what they seem.
Mercy's battle suit is made from a special material I like to call "Cloth Metal". Its cloth made with the elements of strong steel, but is lightweight for battle
You see, I wanted to give Mercy armor for her suit, but the issue is, it could have effected her levitation abilities. If the armor was too heavy, she wouldn't be able to float properly and she needs to be decently protected from weapons.
So I thought blue Cloth metal trimmed with silver would be a nice touch.
And NO. I did NOT pull this out of my ass. This isn't a deux es machina
If you have seen Lord of the Rings, you will remember that chainmail shirt given to Frodo by the Elves. Its exactly like that, only ITS ACTUAL CLOTH.
The Cloth Metal source is also from one of my favorite books "The Silver Crown" by Robert C. O'Brien. Its also one of the weirdest books I have EVER read. And that's saying a LOT
So sorry that you didn't like the suit. But I wanted to explain that even though it doesn't look fit, its not completely useless.
Thing is that it still can't protect Mercy. The thing you want to protect most is your head, your vitals, and your groin area when it comes to armor. One out of three is covered here, but minus extra points for being long, frilly, and VERY easy to grab.