For lvl50 Crafting Guildleves
I suggest that for lvl50 crafting guildleves, they require the player to make one star items of that trade. However the reward should be the secondary material for the 2 star primary mat, EX: Coke for Darksteel Ingot.
Dunno What would be a good way to do the same thing for gathering leves, but something reasonably difficult. Maybe instead of sending you out to gather some quest item under a time limit, they request you go gather the one star items (Darkiron ore for example) and turn a quantity of them in in order to yield the secondary material for 2 star crafting base material (Coke and such).