I do recall hearing somewhere that Burton vetoed the idea of casting Baldwin in Batman since the latter had been 'difficult' during the making of Beetlejuice.
It's a pity because I actually think Burton already had the perfect cast for Batman with his three Beetlejuice leads; Baldwin for Batman, Geena Davis as an intelligent, and red-headed Vicki Vale and Keaton as The Joker.
On the other hand, Keaton was probably a much better match for Burton's vision of Bruce Wayne, the quiet, eccentric, introverted recluse rather than the canonical playboy version of the character; similar to how he envisioned Nicholas Cage as his ideal Superman, the lonely, literally alienated man from another world, rather than the standard All-American boy-scout version of the character.