If Kraft doesn't sue, he can appeal the punishment per recent reports by Schefter (I believe) and others. I think that's his likely course of action.
I'd also like him to support McNally and Jastremski if they decide to file suit against the league for defamation, find them competent council and pick up the tab.
As for Brady, go scorched earth, appeal and sue. Defamation of character is a high bar to clear for a public figure but if he really has nothing to hide then dragging this to court forces Goodell, Kensil, Blandino, Vincent and others to produce their own e-mails and texts. Where did the initial '2 psi under' leak come from? Why did no one correct it when the league had the correct numbers from day 1? Let's get more details around the pre-game e-mail, was Kensil texting with anyone about it? What about game day, when the Colts intercepted the ball, who decided to measure and why?
There's a lot of dots to connect here, and I think the NFL would look like fools if the real timeline and some behind-the-scenes details emerged. Brady's name will NEVER be cleared in the court of public opinion but this would go a long way to at least getting the real story out there, anyone who denies it can pound sand.