From the first spoiler, it looks like this Superdrop might have some really relevant art for this cube.

Blue
This is largely a power-level shift. Removal in this cube is pretty bad, so Ward 4 is rough. The Kappa can also get huge really quickly and is often unblockable, so I think cutting it is a solid call.

• Kappa Cannoneer > Sakashima the Impostor

Black
Oh cool, I finally get a sweeper and all it costs me is cutting a crappy ninja. I can live with that. It's probably for the best that she doesn't batch with any relevant tribes too for power-level reasons.

• Dokuchi Shadow-Walker > Massacre Girl

Colorless
Paradise Mantle fits into the modified deck pretty well and helps with ramp (kind of), which I think is helpful. Also a free artifact for artifact decks. I'd rather run that than another copy of Iron Apprentice anyday.

• Arcbound Worker > Paradise Mantle