I don't think him doing Damian is that far-off from him doing Rocket Raccoon, which he absolutely knocked out of the park and might even be the best thing he's ever done as a creative. He's talked a lot about the reasons that he connected with Rocket and honestly a lot of those apply to Damian as well. I genuinely have no doubt that part of the film would actually be handled expertly under his guide. And that part of the film, which is also the one that's gonna separate this from any other Batman film, is the one that I think is the biggest roadblock in all of this.
There are dream choices like George Miller who'd be great at adapting this material but are kinda far-fetched. And there's also people like Dan Trachtenberg or Leigh Whannell that'd be realistic and efficient (tho even there I don't think it's a given they'd be interested in this particular story), but the thing is that I'm not sure they'd connect with Damian Wayne as a character in the way that it's pretty obvious James would or to handle this particular tone which needs to mix a bunch of really, really specific things. I know James would though, which puts him miles ahead of everyone else.
And the other guys that have been mentioned like David Gordon Green or a TV director or anything of the sort... man forget about it none of those people are actually more qualified and actually more likely to deliver a better film than James on this.
Also like. If the whole worry with this film is it not having a pure creative vision because it's a studio job, wouldn't you rather have a film that's actually 100% James own vision rather than his vision filtered through someone else?