Grimoire cards are acquired based on what you run across in the game. Why would you trade that? That seems fairly pointless. Armor shaders and class items that you don't need can be turned into much needed glimmer -so again, why would you trade that instead? No. I don't think it's a good idea. For some games, yeah, but for Destiny, I just don't feel like it fits with the rest of the game's elements.