1) I really wouldn't want it to be of Japanese origin. Rather, it should be a Hollywood style adaptation in order to have any chance of decent quality. And even that's not a guarantee lol.
2) Don't let Ash and his Pikachu anywhere near the plot. Preferably, it should be set in a more manga-like universe. Actually, a live action adaptation of Pokémon Adventures, with evil gym leaders and E4 plotting to destroy the world, would fit much better than the 10 year old kid meeting two adults with a Meowth here and there over and over again.