I found the StarterList.class file, made a backup (Never mess with files without a backup ) and attempt to add Pikachu to the list (So the starters would be Bulbasaur, Squirtle, Charmander, Eevee & Pikachu)
When loading the client, everything load just fine. It wasn't until I attempted to load a new Single Player that the client crashed due to my addition.
Was I missing a step into the change or is it impossible to customized your Pokemon Starter list without the dev mods doing it?