Ash technically died in the first movie, when both Mew and Mewtwo hit him and petrified him. He was, however revived.
In addition, the Pokémon Crystal special opened up a new protagonist (Kenta, the G/S male trainer) that could be used instead of Ash. The problem is that Kenta's main Pokémon is Bakufuun (Typhlosion), and that runs contrary to the message the animé gives with Ash—that the protagonist must use cute, unevolved Pokémon, or at least iconic mascots (Charizard et al).