Starter change in Renegade Platinum?

I’ve been playing Renegade Platinum and I’m looking to start a monotype run for the game. I wanted to alter one of the starter slots and I tried using DPP Starter and then putting in the starter change code as an action replay (I use DeSmuME by the way) but neither worked. Can anyone give me some advice on a way to change the starters or if I can even do it?