To all whom this may concern:
In response to the above I made a post in the Stainless Steel forum which I am re-posting below:
I've been modding this game and the previous one (R:TW) for longer than I care to remember and I have not found a way to mod the amount of experience gained from killing.
Nor have I ever read any posts from anyone else who found a way to mod that.
What you can mod is the experience bonuses that the various buildings may confer to the troops.
Some hints that you might find useful:
Experience is gained by killing enemy soldiers, not by winning a battle.
The game may show you the average experience of a unit but it does keep record of the individual experience of every soldier in the troop.
So a unit may lose a battle but if there are survivors and they have killed enough enemies they will gain experience.
Likewise, if a unit is of mixed experience, they may win a battle but still lose experience.
This happens if the soldiers that were killed were more experienced before the battle than the ones who survive in the end.
As a matter of fact, experience is both gained and lost during battle, not after it, provided that it is a manually played battle.
For every new experience point that must be gained more enemies than before need to be killed.
This makes the first experience points seemingly easy to gain in relation to the points that make the golden chevrons.
There is a difference in the way battle kills are counted between manually played battles and auto-resolved battles:
In manual battles the soldiers at the front of a unit are the ones doing the fighting, therefore they are the ones doing both the killing and the dying.
So there will be kills that will not count towards the increase of experience because the soldiers that killed those enemies were themselves killed.
In auto-resolve battles the computer counts the number of enemies killed and then divides the number of survivors by the number of enemies killed to derive the kills per soldier.
So only the survivors get credited with enemies killed and they get credited with all the enemies killed - or captured: prisoners caught count as kills.
If you don't mind losing too many troops (maybe you can replenish them), then it seems to me that auto-resolving your battles may be a faster way to gain experience but only for melee troops.
In the original version of M2:TW experience points would increase both the attack and the defense stat of soldiers.
In M2:TWK experience only increases attack: from +1 to +3 (bronze chevrons) it's +1 to attack, from +4 to +6 (silver chevrons) it's +2 to attack and from +7 to +9 (golden chevrons) it's +3 to attack.
In M2:TWK it is possible to retrain an experienced unit in order to replenish their numbers and the new recruits will immediately gain the experience of the veterans.
For this to happen you must make certain that you give the retrain orders right before you end the turn.
If you give the retrain orders, then save, then re-load the last saved game, you must give the retrain orders again before you end the turn, or the new recruits will have zero experience.
In this way it is possible to eventually get an army of very experienced units, but it will take many battles and careful (micro)management of the survivors.
The best way for troops to get experience is to chase down routing enemies.
This is because routing enemies (that are not "fighting to the death" that is) don't cause any casualties to your troops, so every kill gets counted.
For this to work you would need troop types that are fast enough to catch their routing enemies.
Cavalry of course is a prime candidate for this kind of work, especially light (fast) cavalry.
Other troop types that are very good for the "experience building" sport are missile troops and artillery.
I wouldn't expect anyone to have ranged specialists doing the close quarters fighting -and dying- anyway.
As a matter of fact, if you apply the advice in this post you may find yourself extremely annoyed at watching highly experienced troops taking losses.
A tricky thing about missile troops and artillery:
In the original version of M2:TW experience points would increase the missile attack stats as well as the melee attack and defense stats of missile troops and artillery crews.
In M2:TWK experience points increase the melee attack stats and the accuracy of shooting.
That is not something that you can readily see in the unit stats.
But you can observe it in battle.
Experienced archers may have the same missile attack stats as fresh recruits of the same type but they are significantly more lethal due to increased accuracy.
This is more easily observable in artillery.
All of the above mean that heavy cavalry (more difficult than light cavalry to catch routers) and missile troops (lethal at range without taking losses themselves) that have gone into the silver chevrons are going to be your most valuable troops.
I hope this helps.
EDIT:
A question that is in a way relevant to the above was asked by Kilgore Trout in the Skins, Models and Animations forum:
My answer:
If the unit has an armor upgrade and in a certain region they are recruitable with that upgrade, then if you recruit them in that region you will have them with the upgrade.
It is the same with experience bonuses.
Also, you can upgrade them yourself.
If a mercenary unit is depleted of numbers and you station them in a settlement with barracks in a region that has an available mercenary pool, then you can "retrain" them in that city/castle to replenish their numbers.
And if that city has an armorer of the level that is required to upgrade that unit's armor then all of the unit will come out at the next turn fully upgraded.
And you don't need a general to be present in the settlement for that.
Where things become relevant with this thread is with the mercenaries' experience level.
If the mercenary recruitment pool in that region allows to recruit them off the field with a general at an experience level of 1 but your battle depleted unit has reached an experience of 4, then it is preferable to retrain them in the settlement, in the way described in the original post - the same restrictions apply.
In any case, the game can only find the new soldiers for that unit from the mercenary recruitment pool, not from the barracks.
This means that if you have recruited with a general all the mercenaries of that type from that region -or a neighboring region that shares the same pool- then you won't be able to retrain them in the barracks for a while.
Similarly, if there are 2 new units available for a general to recruit but you retrain a previously hired unit in the barracks, then you will see that the general now can only hire one new unit, not two.