I think it would be good if it was similar to the division in a way, now just bear with me here, if you don't already know their gear sets have certain bonuses depending on how many items of that gear set you have equipped, if you did that with destiny you'd be able to mix and match items from certain gear sets and get specific bonuses depending on what you wanted but obviously to get a bigger bonus you'd have to wear a full gear set, I agree with what you are saying but in my opinion my idea might bring more variety to certain gear