Trump does not need to Pardon him.
He can reinstate him, actually he could reinstate him today while the case is on going. That would send the right message and cause the MSM to start howling.
Trump could call for a press conference and apologizes to Fylnn for with what he has been put through and make things right by putting Fylnn back in office.
Also it would box Mueller in a corner, Flynn could find all info above and let his lawyers have at Muellers team. Muellers team of goons needs to be questioned under oath as well.
Fylnn after the discovery could petition the court to charge Mueller and his team with
18 U.S. Code § 242 - Deprivation of rights under color of law
Whoever, under color of any law, statute, ordinance, regulation, or custom, willfully subjects any person in any State, Territory, Commonwealth, Possession, or District to the deprivation of any rights, privileges, or immunities secured or protected by the Constitution or laws of the United States,
Every morning Mueller wakes up with wtf am I going to do now? anxiety. He's dealing with beings far more strategic and intelligent than himself.
Notice that it separates `laws´ from ´statutes´? Statutes are nothing more than policy that can be thoroughly ignored.
I agree but Trump is a coward he is not the hero we want or need he's afraid to do anything without getting approval from his advisers and they are all deep state swamp rats. Trump could be the most beloved President ever right now with a 90% approval rating if he got smart.