I'd just upend the tea table and continue where Returns left off, but vaguely acknowledge Forever and show the passage of time in the film's universe by keeping Robin, though I'd recast him just to avoid being too sticky with continuity.
Hell, I wouldn't even call it Batman & Robin.
Who would you pick to Direct?
Tim Burton. I always imagined a nice, creepy, gothic finale under his vision.
Christopher Lee as Hugo Strange, in a 'secret mastermind' sort of role, eventually he finds himself fascinated with becoming Batman as he gradually slips further into insanity
Johnny Depp as Crane/Scarecrow, operating as Strange's sort of weapon/puppet, he takes over as a bigger threat later after Batman manages to take care of Strange
Michael Keaton as Batman, of course
Michelle Pfeiffer as Catwoman, she sort of haunts Bruce, watching him try to uncover the mystery at hand, secretly helping now and then, and he still hopes against chance to see her alive again someday
(I really have no idea - a younger Tom Cruise?
) as Robin, this version of the character has started college, so he only appears now and then as time passes within the world of the film, to help out with bits and pieces of the cases Batman is on - think early BTAS
I'd also recast Gordon, and make him interesting and
relevant. But he would likely not be as substantial a role as in Nolan's films if Burton was doing this
Michael Gough as Alfred, of course
I'd also like to see the mob make a showing, and Batman threaten and bully them for info. Maybe the Falcone family?
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Dunno, just think it would be cool to see Burton do something like this. Maybe have it Halloween centric like Returns was Christmas centric.
I'm sure anyone interested can fill in the blanks about the story with their imagination. I just made it all up spontaneously thus far.