You have the oprotunity to replace pilachu as the mascot.
The pokemon you choose will be givin a light ball equivilant. A regional form for its evolution if neccesary. A unique z crystal. Tons of merch etc.
the only prequisite is that is must already be viable enough to be the new mascot. Popular or appealing enough to put pikachu to rest as the face of the franchise. Of both the anime and games.
I think jigglypuff could serve as this repacement myself.
Already popular from smash and the OS.