4) Go Easy On The Crossovers
Despite all this talk of having lots of villains involved, it would be best for The Batman if it stuck to simply playing with the Batman mythos rather than trying to work in major roles for other Justice League members.
Obviously, this is the first Batman movie we’ve ever had that takes place in a world with Superman, Wonder Woman and the rest of the gang running around out there. So, on the one hand, that will be what makes this one different from those that have come before and is something that should be made the most of. On the other, the DCEU movies so far has suffered from shoehorning in references to the wider universe at the expense of the films’ internal storyline.
By all means, remind us that Metropolis is just across the water and that Bruce and Diana have a sort of thing, but it would be best for the movie if Batman was mostly left to his own devices.