10) No Killing
This one is obvious, but needs to be said anyway. One of the most controversial aspects of BvS was the presentation of Batman as tantamount to a serial killer, with several scenes depicting him brutally taking down hoodlums in ways that would surely kill them (not to mention plowing into people in the Batmobile). In the film’s defense, this suited the grizzlier, older iteration of Batman that it was going for; one who had suffered the death of Robin at the hands of the Joker and was feeling powerless in the face of Superman.
For The Batman, though, we want to see the character return to his usual no-killing stance. Now that he’s become best pals with Supes, he’ll presumably want to honour him in his death by becoming a more hopeful hero. Likewise, he’ll also have formed the Justice League and fought alongside a bunch of lighter heroes like The Flash and Wonder Woman by that time. Some of their more virtuous tendencies are bound to rub off on him, right?