Im working on same idea, a regular troops recruited in villages as native and noble/veteran/mercenary/mutant troops recluted in castles.
Working on module_dialogs I get it working with a try-troop standing in zendar tavern; this npc gives troops and take money. Now i have to put a "trainer" npc who hire you the units trhough dialogs in hall castles, but now i dont know how to do this, i will try tomorrow...
If anyone knows a easy way it will be wellcome... also a script or dialog to limit this hire units for a bunch each weak...
Cabre
Later i'll add the rusty code im used, I made it using forum tutorials and source code from mburepositary
Sorry bad english, im spanish.