There is no need to dispel the idea that "back channel" discussions won't fly, because there's no point in the back channel discussions in the first place. There was a hearing, not too long ago, where lawyers on Team Brady made their case and said whatever it is they had to say. Not covertly, but directly. To Goodell. In a closed environment.
Any "negotiating" beyond that point would only weaken their position, whatever it may be internally.
The only options, as far as Team Brady is concerned this whole time vis a vis what they say to Goodell and the public is: "0 games or court. Pick." Any "back channel" negotiating would only serve to negotiate against themselves for no reason at all. If Goodell is concerned about going to court, he drops the suspension. If he wants to play chicken, he lowers it to one game. Asking Brady if one game is "ok" or whatever is ridiculous.
When you're buying a house, you don't ask the seller if your offer is going to be "ok", you just make the fucking offer. And yes, I understand the analogy is imperfect, but it's negotiating 101 to act like every offer is your final offer, even if it really isn't. Guessing where the truth lies is entire point. You don't ask the other party what their 'real' bottom line is, because you're making yourself vulnerable and there's no telling if they are being honest, anyway.