I know it's MY hack, but I guess I'm also an over-achiever (aiming too high). Actually, I won't be adding all new Pokemon. There will only be 210 Pokemon obtainable (the amount of Pokemon in my new Kanto Dex). However, there will be Gen III and IV Pokemon in my new Kanto Dex, but I can assure that they won't make the game feel "wrong", since they're Pokemon that are related to Kanto Pokemon, such as Magmortar and Tangrowth. Unfortunately this means the post-game will be very limited, and there won't be something like the Battle Frontier. I'm totally fine with this because I want the focus to be on the main story. (and yes, I'm going to have to overwrite existing Pokemon for the Gen IV Pokemon I'm including. Obviously the Pokemon I'm deleting/overwriting won't be in my Kanto Dex :P )