Quoted By:
Amusingly enough I actually already do this in the main games.
I've owned a Clefable since Leaf Green who I always use on every team and view as my partner. She always seems to pull through for me and never lets me down, and I've had her with me for years. She's pretty awesome.
As for my ace, that'd be my Venusaur, who I've also owned for quite some time and who seems to be capable of pulling just about any trick out of his sleeve to win. Mega Venusaur is just incredible!