Hey guys, so if you notice how McCree calls Echo partner, what if she was someone (he liked) who died and they restored her personality as Echo.
Also, another point is that Echo sounds a lot more serious in the first cinematic, and her voice is totally different and cheerful in Zero Hour, could she be harboring multiple personailities (=playstyles, so like half healer, half dps)?
ummmmmmmmmmm
no
McCree is a cowboy
its a stereotype that cowboys say partner to refer to friends
nothing deeper
So is their shipping name McEcho?
What if they were dance partners in a competition? And Sombra hacked McCrees robot arm so fan the hammered in to the audience…
Edit: This would also explain why Echo asked for his arm in the cinematic. She wants to perform on a stage again.