So I'm sure I'm not the first person who had this idea but I have successfully completed the current version (V12) with ONLY event Pokemon (Shadows, Pokemon you get from quests, ones you find outside of the tall grass, ones you need gourmet treats for, and eggs you find). Shinies cannot be used unless they were one of the listed types of Pokemon (Got a shiny Misdreavus and Growlithe which was cool). It is definitely worth playing the game like this, it feels like you're taking in lost Pokemon and turning them into a fighting force to be reckoned with. Trust me, this definitely makes the game more entertaining and I'm considering doing it in Reborn soon. (Though that one might not go as smoothly)