I see what was meant by the soldier cost/upkeep problem. If cost were reduced though would an early troop rush not be almost unstoppable against a player that is building infrastructure etc?
Perhaps a preferable solution would be to allow the first few troops at greatly reduced price/free perhaps as personal guards for the channeller. Then at least you'd have something if the opponent troop-spams even mediocre units in the early phase.
Or perhaps an Empire:Total War situation whereby citizens are called to arms when a city is attacked. They may be useless but at the early stage so will the attackers be. The 'penalty' would be a loss of valuable citizens to the defenders making an early 'raid' a valid strategy but not a game-breaking one.
The new Civilization game does something like this. I think it's a great idea and is a good way to de-emphasize armies and rushes in the beginning of the game. Each person in your kingdom should have 1 attack and 1 defense by default. When you "conscript" a person, they get training that gives them an additional 1 attack and 1 defense for the most basic level of training. Higher levels of training should give higher attack and defense, just like gaining levels should do. On top of the person's intrinsic attack and defense skills, weapons and armor would add additional attack and defense.
Let's face the facts here. If an enemy sent 15 conscripted peasants at your city in an early game rush and you have 100 citizens in your village, it's going to hurt, but you're not going to loose the entire village if the entire village fights. However, some of the villagers will be unable to fight (too young, too old, crippled, etc) and so you should not get all 100 villagers mounting a defense. Let's say maybe 40% would be in fighting shape and so you would have 40 attack and 40 defense against 30 attack and 30 defense. You would win the day, but would take some heavy casualties.
In this case, the attacker would have gained ground against you because person-for-person, they won out due to the training they devoted to those 15 conscripted peasants. Even though they did not take the city, maybe they reduced your population by 30 where they only lost 15 people. But, also with the odds in favor of the villagers, they may actually have had a bonus to attack and defense so maybe you only loose 25 people to the attackers 15, or perhaps get lucky and break even. Also, you should get a defensive bonus from the fact that your people are fighting for their own families and livelihoods and will therefore fight much more vigorously.
Now, let's say 50 more turns go by and you now have 250 people in your village (some people in the country side heard of how your village drove away the attackers [your village gained prestige for winning] so they flocked to the village for added defense). But, now another attack force has arrived and they are well-trained soldiers armed with metal swords and wearing leather armor. They each have an attack of 5 and a defense of 5 and have been taught to fight in formation. These 20 attackers fighting in formation negate any bonus you get due to overwhelming numbers because their formation fighting allows them to manage the number of people they each face at any given time. They are now fighting your villagers 1 or 2 at a time and have much better attack and defense than any one or even two of your villagers have. They kill 80 of your people loosing only 5 people of their own and finally your villagers surrender.
So, training and weapons should matter a lot, but your villages should be able to defend themselves against a very early rush. If you had trained 10 people to defend the village and they faced these 20 attackers along with the rest of the able-bodied fighters in your village, you would probably have won and saved the village. So you can't just let the villages defend themselves for the whole game, but they should not be helpless or just surrender to any attacking force.
In the late game, with large armies, the overwhelming odds should trigger something where the villages just surrender without even trying to defend. But larger cities where the odds are better due to their shear size should end up triggering actual battles. If the larger cities are being decimated, then at some point, they will still surrender.
When figuring out how the battles go for undefended cities, the game will need to figure out how many able-bodied people are actually available to fight. It should use the number of people available to determine what the odds look like and then calculate bonuses to defense or whatever based on those odds.
Doing things like this also opens up the possibility that you could have racial traits like 'Martial Arts Way of Life' where everyone in your kingdom is instructed in martial arts and it adds 2 to their attack and defense and reduces conscription/training time by 50% (they only need to learn how to fight as a group). Because they spend so much time training their martial arts, it would reduce productivity for everything else (farming, building, research, making money, etc). For example, you could assume they spend 2 days a week worth of equivalent time learning martial arts instead of farming or building or whatever. Thus, their other activities would take a 2/7 penalty.
Another possibility would also be 'Female Warriors' and 'Male Warriors' check boxes which would make more people available to mount a defense if attacked. So, if you wanted all your warriors to be women, you would check just 'Female Warriors'. If you wanted them to be men, you would check 'Male Warriors'. If you wanted both, you would check both. So, instead of only having 40% available, maybe you now have 80% available. Combined with 'Martial Arts Way of Life' it would make a powerful combination that would allow you to not worry about building an army for a long time.
This would add a lot of new dimension to the game. You would have to keep your opponent's capabilities in mind if you decide to attack their cities. If you went up against an enemy with these options, you would know you need to bring a much more powerful attacking force.