The Pokemon Cinematic Universe, now that would be cool.
It's certainly doable, and the main advantage it would have, I think, is that it would look very different from the MCU.
The appeal of comic book universes like the MCU is seeing all the different characters bump into each other and team up. Pokemon isn't really like that. You don't need to try to build up to some big crossover clusterfuck like Marvel did. The appeal of Pokemon is the discovery and sense of adventure from seeing humans exist alongside these creatures. That means you can tell different types of stories in this world and have it all fit together easily because the Pokemon themselves are the connective tissue.
I think that's what's interesting about starting with Detective Pikachu if they do intend to make it a universe; since Tim and Pikachu are detectives, you can throw them into just about any situation in this world and have it make sense as long as there is a mystery to solve. That makes it easy to expand the world beyond Ryme city without needing to throw too much at the audience at once.
Wanna to set up a movie about Ash? Maybe Professor Oak hears about Tim and Detective Pikachu and asks them to assist Ash with some problem.
Wanna do Pokemon Ranger? Tim and Detective Pikachu are called by the Rangers of the Galar Region to help solve a mystery surrounding kidnapped Pokemon.
Wanna introduce Team Rocket (and I mean THE Team Rocket; you know the ones)? Well, they're criminals. They can be the villains in the next movie.
