An idea I had to make Destiny feel more RPG-ish would be to have different types of armor you wear. The armor we have now would be the medium tier. Light tier would grant movement speed or agility at the cost of being a bit more fragile. Heavy armor would make you slower, but you would be able to take more damage. This is a vague idea, but I think it would mix things up and give players options to take on different roles(apart from subclasses) such as tank, glass cannon, etc. The issue I see is balancing it all in the crucible....unless armor pieces had two separate trees to upgrade. One for PvP and one for PvE.