I'm going to bail on the prerequisite that 4-packs be built on an existing figure. If it already exists? Great. If not? Take notes, Hasbro!
SEPARATISTS
B-2 Super Battle Droids
GRAND ARMY OF THE REPUBLIC
Kamino Security Clone Troopers
Galactic Marines (new sculpt)
JEDI ORDER
Jedi Temple Guards (new sculpt)
IMPERIAL FORCES
Imperial Navy Troopers
Sandtroopers
Imperial Officers - Stormtrooper Corps (Black Tunics)
REBEL ALLIANCE
Rebel Pathfinders - ROGUE ONE (all new sculpts)
Endor Rebel Commandos
MANDALORIANS
Nevarro Covert Mandalorians