So this was supposed to be a complete meme, where I was originally going to run back the awful Pikachu/Eevee on purpose, but see how much more it could be optimized with all of the modern strats we have.
However... while routing that, I quickly formed the opinion that Pikachu is actually genuinely pretty amazing in postgame, despite all my consecutive years of famously ranting about how garbage he is in this game. Discharge and Agility go hard, and Agility is already a meta strat because of Shady's Treecko route. Having almost got sub-9 on DS, I would try experimenting more with the yellow rat...