how to excuse the change of casting (in story)

Riight well, its very obvious that both Atreyu and Bastian were recast, because the original actors grew too old. In the second half of the book, Bastain changed his appearance when he appeared in Fantastica, so he resembled an oriental prince, right? Im not saying in any way the new Bastian looks oriental or princelike lol, but lets say when he went to Fantasica in this film, he changed his looks to how he always wanted :) and Moon Child told him that once something starts to exist in Fantastica, it always has been. So he went there, changed his looks, and so always looked like that-wibbly wobbly, timey wimey :) and Atreyu, his Fantastica counterpart, changed to match his real world equilvant :)

Pulling at straws, but it makes the two films directly linkable xD