ORIGINAL: Bullwinkle58
ORIGINAL: Theages
What about only shutting off production, when a minimum number of enemy troops is present (AV check) and / or a certain attacker - defender AV ratio is reached (eg. more than 1:1)?
Anything, in theory, could be coded, but this proposal doesn't have a lot of logical consistency. If industry is inside the city, why would having more troops outside the city stop it from producing? You also get into satellites issues. For example, this gives the defender free intel on the AV strength of units sieging the city. The defender just has to watch for the switch to flip on or off. Also, a lot of units don't have any AV, but are still enemy units which flip hexsides. Finally, bombing defending troops could have the effect of stopping civilian workers from doing their jobs; flipping the switch the other way through bombing. There is already a way to stop civilians from producing--City attacks on the industry. There's no logical reason killing soldiers should stop steelworkers.
The scope of the game doesn't allow for a "realistic" solution.
Now it is all or nothing. Even a single non-combat unit stops production. The other way around the presence of 30 combat units won't impact production even if there was no defender.
I don't think the cities were all surrounded by a wall with all factories etc inside (medieval style). I doubt the defence of cities was done at the perimeter. A stronger defender would move out to engage the enemy before he can do harm to vital facilities. A weaker defender would protect defensible positions and vital points. He would have to give up parts of the city. So the size of the troops on both sides would be important for how much of a given area is controlled by which side.
A single map hex covers a "large" area. It can be assumed the industries' facilities (etc) are not concentrated on a single spot. To have a defender protect all sites of production, he would require a certain number of troops. The more enemy troops arrive, the more troops he would require to hold them all, or just give them up due to the size of troops arriving.
In real life there never was an all or nothing control of a town (if it was defended). It would take the successful attacker some time to capture the town. And that means production facilities would also change hands not all at once but time after time.
If there are enemy troops in the same hex, there should be "free" intel (up to a certain degree) since your troops are able to see them! You should be able to guess, if there are more enemies than you have troops (maybe not AV but troops).
It is also not logical to prevent resource / oil from producing. If the defender has enough troops he should be able to protect those centers.
If the "steelworkers" are forced to work for an occupying force, they would run away, when enough soldiers are killed. If they are loyal, killing their protectors could also make them flee.
Conclusion: all or nothing (current situation) seems sub-optimal
Another approach for a solution could be to include a random factor for each game turn, how many LI, HI, oil etc can produce. Maybe really just random or influenced by number of troops present or anything else(eg. a counter going up in relation to the odds of an attackers attack and going down in relation to a defender's attack)
An enemy at a base, who doesn't attack should not be able to prevent production.