Cultural recruitment
I like the idea of being able to hire troops from another faction, if you have their village or city. But I'm ok if this never gets implemented.
Regular military, Landwehr, and mercenaries
I like the current recruit system, where villagers can only train to militia level, and high level troops can only be trained from fortresses and towns. It makes perfect sense that a lowly villager cannot become a terror knight.
The regular military, Landwehr, and mercenaries system works fine.
Amount recruited
I think people have already echoed this problem. People deliberate pick mercenary camps over other sources because mercenary camps allow you to recruit a lot at a time.
As stated, the simple solution would be to increase the amount you can recruit from towns and fortresses.
In previous M&B games, the relation you have with the village will increase the number of recruits, and also the quality.
In F&S you can continue that, so the higher the relation with the village/fortress/town, the more you can recruit.
You can even further increase the amount you can recruit by using the Leadership skill (more people want to follow a leader), or faction relation (more people want to follow someone who helps their nation).
Ranks
I think all troops should go all the way to elite rank. I don't understand why only mercenaries from camps can reach elite.
Mercenaries from taverns cannot level at all. I think they should be able to go to veteran rank as well.
A crazy idea would be that the Trainer skill can only level troops to veteran rank.
Troops can only reach elite rank by getting experience from combat. That would make the elite rank more special.
That way even village militia should be able to reach elite rank, because if your villager army can beat a well trained army to level, that means they are skilled and they deserve the higher rank. At that point they are no longer just a bunch of villagers, they are well-trained assassins if they can beat a Lord's army.
Making elite rank only reachable through combat experience sounds like a good idea, that encourages the player to keep fighting.
Customizable gear
This sounds really hard to code, but I think there should be an option to customize the gear of all troops, instead of just mercenaries from camps.
Village militia should rightfully have low stats compared to better trained troops from the city. But if I want to give them really powerful gear (provided they have the stats to equip them), I should have the choice to.
The initial cost to replace equipment should be high, but the wages shouldn't increase, because I have already paid for the equipment. When I pay wages, I am paying for their skills, which is low.
Morale
I like the idea that mercenaries are cheap, but they have low morale compared to city officers and are more likely to rout.
The higher the rank, the less likely they will rout. But mercenaries should be relatively easier to rout compared to regular troops.
I liked that in Warband, if your army consists of units from a faction you are at war with, the morale would be lower.
Other
I have a crazy idea where a specific type of troop will cost little to no upkeep.
I think it was in Medieval 2: Total War. Town militia when put in towns, would cost no upkeep. They are not that skilled, but they help you save costs.
This will add new strategy to the game, where instead of everyone using Winged Huskars, people can opt for strength in numbers at little or no cost.
Problem
I encountered a slight problem at the start of the game. I could only recruit mercenaries from taverns and camps before I joined a faction. Mercenaries from taverns cannot level, and mercenaries from camps are very expensive. It gave me an uneasy feeling that I only have a mediocre army with high wages.
So there are limited choices for someone who doesn't want to join a faction yet.
I think you should be able to recruit villagers straight away. I don't think it will be a problem, because village militia are not that powerful anyway.
But there needs to be some option for a mercenary player to have a powerful army. Allowing the player to customize the equipment of village militia should be a reasonable option.