The reason I'm not a big fan of having the number of attacks tied to the number of citizen defenders is two fold:
First, as was pointed out--there's the issue of needing to have the city defenders in place before you end your previous turn, otherwise, as was already asked, 'what's to stop a person from just converting all their citizens over to defenders right before beginning city attack?' I think this will be a headache in practical terms.....it will require a player to remember to go into his city and rearrange citizens before he ends his turn and then rearrange them after his turn....and back and forth. In practical terms, I don't like the effect on gameplay. I also don't like the prospect of reloading the game because the player had an oversight and forgot to move citizens into defense slots.
On the other hand, if the number of attacks is tied to building construction and (maybe but not necessarily) to SPs, then the player never needs to worry about moving citizens into defensive slots. The player will always know that his city has 1, 2, or 3 attacks.
The player will only have to worry about moving citizens into defense slots if it is apparent that he is being faced with force that city attacks alone cannot handle. Also, a player would be able to move citizens into defense slots as need be, and it would be the same as garrisoning a unit now....move the citizen into a defense slot and the effect is immediate. End your turn and move on.
I think the color of defense rating number, which appears above the city, should change if city defender slots are being used--to remind the player so that the player isn't using slots needlessly because he forgot.
Second, if number of attacks is tied to defender slots, then the attacking player will be unable to predict what extent of city defense he will face. Whereas, if the number of city attacks is tied to visible buildings (especially), then the attacker will know from looking at the city how many attacks it has. If the attacker sees that the city has built a castle, then he will know that the city has two attacks. And so on....
I do kind of like this idea, but I don't know if a straight, minor defence rating increase merits a specialist on its own. Other specialists can significantly increase research speed, or gold income, or production; city defenders would give..... a small % increase in the city's defence rating.
These citizen defenders are not specialists. They are emergency conscripts. They are citizens who have been pressed (or volunteer) to fight for their city.
Note that raising the city's defense rating also has the effect of raising the city's attack strength (right?). Thus, the city can hold off an attack longer and inflict more damage, but at a cost of lost growth and production, which makes sense because instead of manning fields and mines, the citizens are manning walls/castles/armories, and dying in skirmishes against the attackers.
a small % increase in the city's defence rating...is just completely useless...a relatively minor increase in city defence.
Balance is the key here. Obviously it would take some playing around to figure out a good balance between increased defense, cost to defending city, and burden on the agressor. But, I do think a good balance could be reached.
Again, note that the benefit isn't just city defense, but also a boost to city attack. But, if I'm wrong about that, then it could be that each city defender increases city attack by 5% or something.
I will say this though---if the balance were slightly weighted in favor of more slots at lesser increased defense rating, then the player would have to move more citizens over to defense, which in turn would raise the cost to the city, which in turn would lead to some very interesting siege warfare. Literally, an attacking army could adopt the strategy of trying to absorb the damage and minimize losses in exchange for starving the city into surrender. At this time, this strategy doesn't exist.
With this system in place, possibly we could do away with the built in mechanic of half the population being killed by taking a city--with this system, there may be a lot of circumstances where half the population died in defense of the city, therefore the aggressor simply takes the city as is.
even a newly founded 1-pop city can attack multiple times per turn, and if you purchase a couple of defensive buildings, it instantly becomes incredibly powerful. Also, giving all cities extra ranged attacks this way would only make the current problem
It would makes sense that a city that has constructed the most powerful available defense systems would be able to utilize such technology right out of the gate. To minimize this happening though, simply raise the cost of the buildings similar to how the devs have played around with the cost of happiness buildings and courthouses etc.
Also, more attacks doesn't translate to more
strong attacks, since the strength of the attacks has other factors involved, such as population. Also, with only one population, a player couldn't take advantage of the slots available for extra defenders. So, I doubt there could be a situation where a 1 population city, standing alone, could be very powerful even with the most modern defense technology.
Besides, if this became a problem, then the devs would simply need to increase the importance of population number in determining attack strength of a city.