Here's a few ideas ive come up with. Some of them may be overpowered or weak but they are still strategies that should be considered in the game.
1) Experienced General.
+3 ARB to all units in general stack
+3 HP to all units in general stack
+1 attack to all units in general stack
+1 defense to all units in general stack
+3 movement to all units in general stack.
+50 cost to transports
+100 cost to air transports
+20 cost to bombers
2) Anti-Stealth Fighter
+2 to stealth detection range
+3 to view range
+1 defense against marines, stealth planes and subs
-1 attack to tanks
-1 defense to infantry
3) Hybrid Warfare
+3 attack, +2 movement, -10 cost to militia
+1 attack, +2 movement, -10 cost to infantry
-3 attack to tanks
-1 movement range to transports and air transports
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Don't trust the manipulative rabbit.