Just had a thought - The cat infantry don't have any native penetration, right? Can they even damage higher level enemies? You'd need an armor-shred light tank or Wendy's active skill. Seems you'd have an almost fixed selection of front line units at that point. BTR-60, M3-Halftrack, Flammpanzer 38, PT-76, T-70. Maybe AMX-40 or an infantry unit if you have the perfect storm of emblems for it.