Additive Advantage [5th Edition House Rule]

On the whole, I am a fan of the new edition of Dungeons & Dragons. However, my gaming group was not fond of some aspects of the Advantage/Disadvantage rule; they felt that the current Advantage/Disadvantage rule (as of the final playtest packet) goes too far in abstracting the combat situation from reality. This is my first house rule, then: a change to Advantage that preserves the game math while also making Advantage more dynamic and interesting.