I have fewer issues with always using Ash in these things, and more of a problem with them just making it dark, and more violent rather than a story that's actually interesting. I would pay many times over if I was given a mature story of the characters I grew up watching and playing, especially if it was done as a sort of ending, some amount of closure for the characters.
What I'm saying is I want a Pokemon "Dark Knight", not a Pokemon "Transformers".