The idea is simple. I would like to customization options linked to your actions(explained more further down)

I am bored of seeing game gluing their unlock system on credits and exp. It really limits the possibilities. Also it creates no emotional response(or any kind of response for that matter) seeing someone wear a cool outfit when I know he just bough it. It really means nothing. I remember back in Halo you had to accomplish something to get a customization option. Doesn't matter if it was something small or the infamous hayabusha but then outfits meant something. Know that the technology is years ahead and it is decided that For Honor will have a campaign and fairly good customization system I think it is time for It to be revived

Here are some ideas as for how to unlock outfits,armor,etc. Defeat a really hard boss while taking no damage. Defeat a boss only with light attacks. Defeat a boss by using the environment. Complete a mission under a specific time limit. Complete a mission by killing no minions. Complete the game on its hardest difficulty and so on... This are not set in stone and can be mixed and matched. It would be cool to see every boss to have a challenge for you to complete and a linked unlock for your multiplayer matches. But I think everyone gets it by now so I will stop here.

This system applies to everyone. People that want to look different will like this feature because it won't be as easy to unlock all customization options. Game completionists would like this feature because they could see their efforts on their outfit collection. Even casual players would enjoy the variety. Most importantly developers should love this because it would improve the longevity of the game without forcing the players to grind multiplayer matches for credit. This means better enjoyment

Well I think I made the point just let me say that the black knight skin should be the hardest one to achieve. We all know how it turned out in Chivalry...