Standing Armies and Feudal Levies Mod

I think the recruitment system could be made a lot more realistic in M2TW. I've had an idea on how to do this, so I'm looking for some opinions.

Basically, each region would have 30 or so mercenaries available at one time, designed to give a realistic representation of knights, levies, peasants etc in battles. 30 units instead of the standard army of 20 would allow for a little variation in the armies. These Mercenary units would have low hiring costs, but very high upkeep costs, so they would have to be disbanded shortly after use, representing fuedal levy armies.

As-well as this, standing armies could be created at castles and cities. For these units, they would have very high recruitment costs, but slightly lower upkeep costs than mercenary recruited units.

This system would mean guaranteed realistic armies, especially in the early game, with standing armies not appearing till later except for the wealthiest factions, such as the Byzantines, as is realistic! The standard western European levy army might be 4 Knights, 8 Militia type units, and 8 peasant type units, for example.

Any ideas on this mini-mod plan?

I'm planning to do something similar in Anno Domini but without using mercenaries but having different "feudal" units with very low cost of raising and upkeeping... until they stay into settlements. When they move around the player will have to pay lot of money following a coherent system (it is already done but need tweaking and playtesting).

Unfortunately this huge modifications will have to be done for the player only as AI is unable to disband and to manage things efficiently, so they will just have some cheap troops (and we all know how much it is needed due to the poor selection usually AI put in the field anyway).

Yes the problem with a scheme like this is the AI.

My plan is to have the castles provide a number of free upkeep units, which would be units such as knights and levy/sergeant spearmen to represent their retinues. The initial payment cost of the unit represents the land given to be worked by those nobles/knights (since the cost of their equipment is their responsibility) but they are free in upkeep if garrisoned at the castle from that point to represent their feudal obligation, however their replacement rates would be very low. This sets them apart from the 'standing' armies that must have their upkeep paid for.

Note that if these 'feudal' free upkeep units end a turn away from the castle, their upkeep must be paid (and it could be higher than normal) to represent the fact that their feudal obligation is really only for 6 weeks or so. However if a campaign is kept close to the castle their cost of use could be kept very low.

Only certain units would be designated free upkeep, not all units able to be produced by the castle.

I am working this into my EDU and EDB files currently.