dual color/style cards
With each color being its own wheelhouse of mechanics, dual color cards allow for control points in which one color is able to share its signature mechanics with another color, as well as having cards that employ the mechanics of two colors that otherwise wouldn't be able to intermingle.
Thematically, this is where we get to do fun intersection stuff. With the idea that each style is its own community of players with its own established ways of playing the sport. This is where we get into cards that illustrate them borrowing ideas they like from other styles. Particularly with balloon classes.