I'm almost certain Byrne had priority on the psionic aspect. He mentioned his POV on Superman's powers many years before while he was still at Marvel. He even did a trial run of the idea in FF #'s 249 - 250 ("Man and Superman") with Marvel's Gladiator. While Moore might have done better justice to the psionic aspect, I do believe Byrne was the originator. (I may dislike Byrne's writing intensely, but I do try to be fair and objective.)
Huh! Well, I'll be danged! I have the issue you're talking about - FF #250, which came out in 1983. And you're right - this idea is present there.
However, this does not prove John Byrne had this idea first. WARRIOR #1, the first appearance of the Alan Moore version of Marvel/Miracleman, came out in 1982, and Alan Moore had printed quotes detailing how he would write Miracleman that were floating around in UK fan magazines as far back as 1981 in
the Society of Strip Illustrators Journal, which was how he was approached by Dez Skinn to write MIRACLEMAN in the first place.
(Yes, it took until 1985 for MIRACLEMAN to make it to the United States thanks to Eclipse Comics, but one of the reasons that sales were not as impressive for those comics was, everybody that REALLY wanted the Alan Moore/Alan Davis MIRACLEMAN had already bought the UK WARRIOR issues).
If I might bring up a piece of circumstantial evidence:
Byrne, working by himself, has never created a worthwhile or memorable original character in his entire career.
He has never created a worthwhile or imaginative concept to transplant onto existing characters in his entire career: from the Vision having no emotions to not "really" being the Human Torch, to Namor not really being an honorable, complicated regal monarch with a legitimate grievance against the surface world, but instead having a disease that "makes him crazy" every so often; to Byrne's catastrophic relaunch of Superman whose flaws have already been detailed in depth by many people on this very website. Individuals have spent careers undoing the mistakes Byrne has left behind; saddled with the detritus of Byrne's FF run, the reason Alicia acted as wildly out of character as she did in Byrne's run is because "Byrne's Alicia was a Skrull." Look at Loebs bringing back "classic" Superman elements, or Busiek restoring the Vision's humanity and original origin.
So, in that context, excuse me if I'm in-
freakin-credulous of a claim that it was Johnny Byrne that originated a concept instead of
ALAN MOORE. That's sort of like saying, "I'm positive the man who stole my purse wasn't that known, convicted pursesnatcher. It had to have been that elderly church lady." It doesn't mean that the pursesnatcher is innocent and the old church lady is guilty, but
come on.
I will give credit to Byrne for one thing: he ripped off MIRACLEMAN before it became fashoinable to do so.
I was not aware Elliot S! Maggin created LexCorp. Seriously, if they don't cough up the bucks, Maggin ought to get an attorney. True, Jack Kirby never got his art back from Shooter, that's in the past; Stan Lee recently won a giant settlement against Marvel for over several million dollars, and that was from a pussycat like Stan who didn't really push very hard.
And it's even more damning proof that Byrne is the exploding syphillis canker that we know he is. He shamelessly robbed the desk and concepts of a writer
that was fired to make way for him. A writer, incidentally, that was powerless and marginalized and had no voice to really defend himself.
There's a certain vindicating thrill when you find out that people whose work you despise are also worthless, evil jerkholes as human beings, too.