Well hm. Ok. I guess to me this makes a lot more sense as something you do for a spinoff movie. But I do agree it's probably an easier/cheaper thing to make. I just have a hard time getting over the fact that a movie franchise built off the "regular universe" has a lot more potential both as a movie and as a crowd pleaser. It would be truly unique whereas what I'm hearing about Detective Pikachu gives me Alvin and the Chipmunk or Garfield vibes when put in to movie form.
Honestly, as far as live-action Pokémon movies go, Detective Pikachu was probably the best course of action. That said, the idea is a bit recent, so maybe it'll allow Legendary to get creative with the concept.
Hopefully this means that we'll get a localization for the game to coincide with the movie, but I suppose the 3DS would be long since dead by the time the movie drops.