With regards to Shaders, I believe that each would have a cost that related to how rare the shader was and/or how much glimmer the shader costs to apply to a weapon. In fact, they could decrease the cost of applying shaders when implementing this, while keeping the cost of buying them relatively high in comparison. This way, there's an option to buy them, but it'll require much more glimmer than going out and finding them in the world. In addition, special shaders like the ones from special events, trials, and raids could require tokens to get from the kiosk. This way, there's a collection aspect of gathering shaders, it frees up vault space, AND players get the option to buy shaders without having to redo an activity every week to save up enough for their full set of armor and possibly weapons.