Will Smith is the best. I'd support him in any traditionally white role so long as being white isn't somehow integral to the story (like the story of the Klan, Hitler ...)
Casting anyone related to Batman as Batman Beyond would be a fucking unnaceptable tragedy as it would give legitimacy to the bull fucking bull fucking shit shit that is the Justice League episode where that douche who I now can't diss too much because he died who had nothing to do with Batman Beyond just retconned that bull shit genetic link in there and marginalized everything that Batman Beyond stood for.