As of now, hiring NPCs are a tad underwhelming to say the least, as they are overly suspicious of players, refusing to let them hire units unless they have "proven their worth" to their faction/ fiefdom. As captains/chieftains/lords of their factions, it is likely that they themselves have earned the respect of their faction and troops with their own heroic feats, rising to the top as military commanders skilled in combat. However, in combat, they are not much stronger than the average soldier, only having a slight health boost and only attacking after the player attacks them, almost always giving the player the upper hand. As such, I suggest, a possible re-working of such npcs to improve their combat prowess and re-introduce them as potential faction 'minibosses', instead of simply being seen as 'free 5 alignment' by enemy players
New potential mechanics
For one, hiring npcs should be much more durable than the average soldier, which can be done by either increasing their hitpoints by at least 1.5x - 2x the health of regular soldiers or giving them a base increase in armor points to balance the lack of headgear for some of these npcs like Uruk Chieftains and Lindon Lords just to name a few. Their many years of combat experience have hardened them into veterans, capable of hitting harder and moving faster than the average soldier.
As skilled tacticians and leaders, they should have the command and respect of the troops of their respective factions. This could give rise to a few mechanics. One potentially exploitable idea would be that attacking a hiring npc would spawn in a wave of level units for the faction to aid the captain in battle, potentially bringing in new waves of units after the captain's health pool is reduced by a certain amount. Another mechanic would be that attacking the captain would 'alert' surrounding allied units within a certain radius that will rush to the captain's aid.
Additionally, as army leaders of their respective factions, it is unlikely that these npcs would stand idly by as a player with negative alignment invades and pillages their lands. As such, I propose two types of captains, both with the aforementioned mechanics. One would be the hiring npcs that we know and love, defending their camps and citadels from invaders. They will step in to defend their structures after being first attacked or if their soldiers are killed near them, much like how they currently behave. Another type of captain is one who specifically leads their troops to challenge a player with negative alignment. For example, if a player with negative Lindon alignment wanders through their realms, trying to get elfbane for their newly-attained warhammer, they could possibly trigger a new event, where a message in the chat would announce that "Nellas, the Lindon Lord challenges you!" This would spawn in a Lindon Lord and multiple Lindon warriors and banner bearers near the player that would immediately engage them in combat. If defeated, they will not respawn, unlike regular npc captains, and if the player is defeated, they will wander around the area for a short while before withdrawing (despawning).
New speech lines
Of course, if such new mechanics are implemented, such npcs could potentially get new speech lines, including when summoning warriors/ calling for aid. Some examples could include:
"Sons of Durin, charge!"
"Come lads! Let us crush these buggers!"
"Men of Gondor, hold fast!"
"Sons of Gondor! It is time to prove youselves in this hour of doom!"