Most of the legendaries involve some kind of tradeoff.

I really dont want to give all whites and greys to the goblin. This makes the goblin not useless as most of the whites he takes will be returned, allowing players to still have their goblin, their whites, and possibly legendaries if the goblin feels nice. So the Goblin will grab a white off the ground, then throw the item back out, with the chance of it being white, blue, yellow, orange or green.

Maybe instead of collecting white items the Goblin merely trades them.

What would really be cool is a change to the puzzle ring. Trust me though, clicking through those racks in act 3 will yield plenty of common debris. People have be trained so long to ignore that shit that it take a little effort to remember to click and gather them for the crafting mats. You have to make a point in clicking them in order to collect your white items. However I will point out that whites almost always drop from armor and weapon racks throughout the game. The Common debris it just too important for crafting to ever be worth the goblin stealing all your whites. It sounds great as an idea, but in practice it really doesn't work out.

Diablo 3 puzzle ring drop