I have googeled, and found the same results. As I said, I am new to this, and hoped there was some tools I could use.
Anyway, I managed to change the starter pokemons, but the rival will now only pick chicorita, like menioned in the forum you linked to. Also, I can't manage to change the pokemon description when you pick a pokemon.
When it comes to type effectiveness, I haven't tried yet, but I smell a potential issue. If I want to add or remove type effectivenesses, it will require less or more space to save. Is there any problems I might encounter if I change the ammount of effectivenesses?
Thanks for your time btw.