Levitz is a good name to throw in the ring, but again, maybe too much of a comic book purist for some people?
I mean, I know a lot of people who refused to even see Justice League because John Stewart and Hawgirl weren't in it.
I know it's because they grew up watching them in a cartoon show, but seriously; across every single incarnation of the JLA, they've got like ten minutes of active roster membership combined. There's about a dozen characters who "deserve" to be in a Justice League movie before
those two C-listers, BUT, a lot of people were pissed anyway because it's what they grew up with, even if it's wrong.
Levitz takes DC canon VERY seriously, so I'm not sure he'd be flexible enough to accommodate the broader fanbase. As I said, that's generally the problem on the DC side. Geoff Johns knows the canon - there's really nothing in the GL movie that isn't hard canon, it's faithful as hell but just tonally a bit of a misfire - but "knowing the canon" doesn't seem to be enough for some people who identify as DC fans. Or Zack with MoS; I can pretty much recite chapter-and-verse what every single frame of that movie was cribbed from, so "fidelity" was not that film's issue, but people apparently wanted brighter colors more than they did a reverent and faithful take on the canon. But who could have guessed that before they got to market with it? They thought making it exactly like the comics was all they had to do, and they did that; then they got yelled at for "problems" that they hadn't even planned on becoming issues.
So Johns is out, Snyder's out... pretty much anyone who KNOWS the DC canon and takes it seriously probably wouldn't be willing to compromise enough to get anything done. Lots of guys would be great for it in theory - What's Mike Carlin up to nowadays? - but in actual practice? Ehhh... Again, which fans do you bend over for, and why, and how far? It's not an easy assignment. I know I, personally, would want a DC "expert" in charge but they've tried that and it didn't work. I know I definitely wouldn't want a neophyte at the helm, but some people claim that's exactly the right approach because then they can just make populist films that are safe and generic blockbusters without being beholden to any source material. I strongly disagree with that, but its certainly some peoples' opinion.
Grant Morrison does way too much acid to ever be Head Guy of anything at all.
But I agree, definitely let him in the Writers' Room. Just take absolutely everything he says with a giant shaker of salt. He's a great ideas guy, but... well, if Final Crisis has shown us anything, historically, it's that some things can be even more divisive to DC fans than Zack Snyder movies.
And I actually LOVE that whole deal, I will forever maintain that Final Crisis was f*cking brilliant and I'll defend it with my dying breath if need be, but "populist" it most certainly was not.