It's not "a single archer" conquering a city of 5000. That archer represents a unit with lots of men. It doesn't take a lot of armed soldiers to occupy or take over a fairly large population.
Since all your units are coming by taking population and training them, it may actually be one archer. We don't know what the minimum numbers are right now.
It's biased towards helping those that leave defenses thin or non-existant.
It's really not, since you're talking about something pretty bad and expensive to do.
It's a game mechanic that can easily be replaced by always having an ultra-cheap 1-turn unit that can be produced.
As Scoutdog said, not with the mechanics of training units in Elemental. What we're talking about is taking whatever weapon stockpile you have access to in the town and using it all to immediately make whatever you can.
Or, perhaps better, replaced with a mechanism like Kohan where cities and forts have an inherent defense force so it's automated.
That might work too.
It's only value would be in the early game when unit strength differentials are low, unless you plan to have conscripts get better over time.
The equipment you're making improves as you get more resources/research/production/whatever. So naturally the militia you make with that equipment is also going to improve. The only difference between normal troops and militia is that one of them has training, and the other doesn't.
edit - It's probably worth mentioning that a "cheap unit you can produce near instantly" is exactly what we're talking about here. If you make a unit with no training, it should take as long as it takes to hand them a sword and say "pointy end goes that way".
