New guy chiming in here, FWIW.
As many others here keep trying to point out, when it comes to court, Brady (and the union) have to challenge that actions of the league were not in compliance with the CBA, not the findings of the report. Then if the court decides the league acted improperly they will force both sides to do something different. It's not likely the court is going to allow a whole new Wells type investigation simply because Brady doesn't like the findings of the first one - especially since Brady was clearly non-cooperative during the first one. So about the only thing left is for Brady to convince the court that the appeal was tainted by having Goodell hear it. That's an uphill climb for several reasons, the first of which is the CBA clearly states the commissioner will hear any appeal.
Now, this is where Vilma won in court by saying Goodell was so involved with the investigation and since Goodell handed down the punishment he couldn't possibly be unbiased during an appeal. But this time around Goodell has been more careful about all this. He hired Wells do do his thing and then, more importantly but we're all ignoring it, he actually had Troy Vincent hand out the punishment to Brady. This is going to be a whole extra wall for Brady to climb when arguing that Goodell could be impartial and shouldn't have heard the appeal. We like to say Goodell gave the suspension but technically it was handed out by Vincent and then appealed to Goodell.
But even if Brady wins the right to a new arbitrator, there's no guarantee he will be exonerated. The letter from Vincent states 3 different reasons for his suspension. The first is that it's rather obvious Brady was aware of the actions of McNally. The second was his refusal to cooperate and the third was the fact that Brady was caught lying during his interview but then refused any more interviews in order to clear things up (non-cooperation when caught lying).
These are the reasons given by Troy Vincent for Brady's suspension. It's about a lot more than just the lack of 100% scientific proof, and who's going to convince, firstly, the court, and secondly a third party arbitrator, that the decision by Vincent to suspend 4 games and the upholding (possibly) by Goodell upon appeal was done improperly based on their reasoning above?
The only thing Brady is going to win in court is a new appeal to a different arbitrator and a delay to his suspension. History says he may have good luck with that, but as many have mentioned, that could also result in him missing games late in the season instead of at the start. And if he somehow does win the right to a trial of any kind then yes, the league can subpeona all sorts of things as well as get McNally and Jastremski on the stand. I don't see that happening.
And my final thought requires a certain amount of conspiracy theory but I suppose there is some possibility of it happening.
The only other thing I can think of that Brady could have up his sleeve is if he threatens, as Belichick did with Spygate, to expose all of the cheating that goes on in the league. Depending on just how much that is it could be a serious nightmare for the NFL. it wouldn't do Brady any good but if he threatened and actually went through with it he could always retire to the Galapagos or someplace with his and her millions without ever looking back. So it could be a semi-bluff of sorts, especially if there's any truth to the supposedly covered up elements of Spygate that were never made public.
League: Look, we know cheating happened and we have to protect the integrity in the public's eye. We have to give you some kind of suspension.
Brady: If you suspend me I'll tell the whole world everything I know about Spygate and everything else you covered up. That will cost you billions and I'll just disappear.
League: No, don't do that. Let's meet again tomorrow . . .
Yeah, that's out there. But then again if the reports that the two sides are having meetings is what the delay is all about, but Brady is dead set on total exoneration, then what do they have to meet about? Hmmm . . . . I wonder.
And that's my new guy $.02.