Assume there are regions with tons of trainers like in the main games as well as Pokemon communities like in the Mystery Dungeon series. And you could choose which Pokemon you'd want to be.
Personally, I think I'd rather train Pokemon. Being a Pokemon would come with additional strengths, but also weaknesses, and as a trainer I could still interact with all the Pokemon I wanted. Plus, I'd run the risk of being caught as a Pokemon.
Oh, and say which Pokemon you'd want to be if you picked that.
Why do people... betray one another? They might as well... all just die instead. Welcome to my kingdom!