So, I don't think this would fly in D&D, but I briefly considered for a very house-ruled and streamlined version just making things give you a bonus or penalty. No type, no varying amount. You do a cool thing that helps a friend, you gave them an attack bonus. Great. They get +2 to that.
Someone else does something cool to help their attack bonus? Doesn't stack. They took a feat to get an attack bonus when they do something? Doesn't stack. Who cares, just play the game.
But I really wonder how many people could cope, or if folks would instantly rebel from the simplification.
I imagine that we'll have a variety of bonus and penalties, of varying amounts and types, and the advantage system is a mirror for combat advantage and intended to be a non-stacking simple bonus you can get some of the time. Whether that's by flanking, or describing your attack really well, or reiterating a phrase (ex: "I am Inigo Montoya, you killed my father, prepare to die") to improve your morale or harm your enemy's... but basically it's circumstance bonus, but far more common and codified.
I can live with that. Whatever the name.