Or you could just have Jeskai Ascendancy instead of Paradox Engine, and any zero-drop that goes to the graveyard instantly draws your deck, puts any cards you want in the graveyard, makes infinite power attackers, and thats probably enough
If not Belle, pick a similar engine that converts board presence into resources
Manaphy perhaps speaks for itself with the ability to shield your benched Pokmon from harm, something you'll want to take advantage of, as your benched Pokmon will be huge targets for your opponent since they're vital to supporting your Greninja Ex
Sami, Wildcat Captain Sami, Wildcat Captain is extremely costly for a cost reducer
The lid doesnt clip or slide on and off, as is common, but is held in place with strong magnets, making opening and closing super convenient
Its also an affordable commander to build around that can be easily upgraded