What I hope happens behind closed doors is the Vlade sits down with Cousins and just talks. No agenda. Not trying to "fix" anything. Just talks. And listens. Just get a feel for how your guy feels, and what he wants. Cousins is human. Hear his story. Begin to gain his trust, slowly. That's how any of this healing must begin. Once Cousins feels heard, and you know how he feels and what he wants, you can begin to build bridges where they need to be built.
Also, if there is any hope, Vivek must absolutely cede all power to Vlade, because I think that is where the real mistrust lies (Cousins to Vivek). It's not so much that Cousins' has personal mistrust of Vivek (although I'd bet there's some of that), but it's that he has professional mistrust of Vivek. Keep in mind Vivek is Cousins' "boss", and essentially has a large amount of control over how his career unfolds. I would understand if Vivek appeared to Cousins as not only almost completely incompetent, but also lacking the humbleness and self-awareness to recognize that. The owner-meddling-with-a-future HOFer's-career has got to scare the living crap out of Cousins. Vivek's not racist, but the Sterling example is always in players minds of how much power an owner has to **** up a franchise.
Say what you want about Cousins' behavior, but one thing he absolutely never lacked in was self-awareness, and knowing his strengths and weaknesses. My guess is that he despises people that don't share that skill/value.