hmm... I wonder... my understanding of Zone of Control is that it negates the ability of attackers to attack from any but one plot (which goes unmarked which is terribly frustrating!) I wonder if this means that when the S&D processing runs its check on combat strengths on adjacent potential attackers that they aren't evaluated anyhow due to not being 'potential attackers' since they are standing in plots from which they may not attack? In a sense, this might be negating all S&D bonuses brought against the city by default. That would be something to investigate.
As for Traps and Dynamic Defense...
I could see traps adding to a general repel factor in the city (not by unit combat so I'd have to do up a new tag for that) but not so much for Dynamic Defense. There's a difference here:
DD(Dynamic Defense): The % of reduction of an attacker's compiled Surround & Destroy bonuses.
Repel: The % chance that the attacker is forced to immediately withdraw upon the first round of combat, in which the defender deals damage, after all first strike rounds.
Repel does sound like a good idea for traps as an approaching unit may find their approach needs serious re-evaluation due to a failed attempt to cross a trapped region.
Since any flat iLocalRepelModifier (which I'd be happy to add to the dll right away) would be a modifier to the defender's repel values which can also get fairly strong, I'd keep it to a level of moderation, something like:
Pit Traps (Mining) = 10 Local Repel
Mechanical Traps (Machinery) = 20 Local Repel
Landmines (Mine Warfare) = 30 Local Repel
Booby Traps (Guerrilla Warfare) = 40 Local Repel
Robotic Traps (Military Robotics) = 50 Local Repel
We'll have to immediately start reviewing our units and promos for applying the Unyielding ability (fearlessness in the face of danger) if we start using Repel. And we'll have to add some promo lines for adding Unyielding, and perhaps some Repel ability (which is an ability intended for Archers, Guns, Defensive Siege, Spears and Chemical weapons (including natural ones such as the Skunk)).
I'd also figured we'd want to have wall and castle addons such as Battlements, Murder Holes, Arrow Slits and Portcullises add to the Repel abilities of Archers, Throwing, (and to a lesser extent Gun units as well). I realize we have some of these already. Gates and Gatehouses could add to the Repel values of Melee defenders.
The thought carries along though too... if the unit is NOT repelled by a trap building, should the trap building then add a free chance to deal some damage from the trap itself to the unit once the repel attempt fails or is overcome? That would be a whole new factor for the combat mechanism and although makes sense, would tweak the odds in a way that would be hard to account for.