Essentially, I wanted to create some more bandit variety within the game because, while the base bandits are fine, it felt like the idea of them being upgraded to culture specific troops was okay but limiting in creativity. So I decided, despite my lack of experience in any form of modding, to see if I can create bandit troops of my own. Each has their own unique tree (some loadouts will overlap with genders), and all of them lead up to tier 6 units. I want to thank the guys over in the ATC Troop Changer Mod discord for all their help - really could not have done this without them! Keep in mind that I am still working out the kinks in loadouts and balance, but it is doubtful that any mod like this would ever be considered balance in the first place.

Requirements: As far as I know, this mod does not require anything else. But it may be safe to just run it with the basic Harmony, Butterlib, etc.

What it contains:
Each bandit type (looters, mountain bandits, etc) will have 2 additional bandit troops - one male and one female. Each new type follows a certain thematic which may break/support the lore of Calradia. They go as follows:

For Looters: Refugees/Vagabonds: In a world where nations are constantly at war with one another on the map, looters find ways to take advantage of the chaos...others follow suit because they have no choice but to run and fend for themselves. Under your command they will return to society as defenders of the peace and the defenders of your household.
The Refugees and Vagabonds are the more versatile of the 6 types of bandit units when referring to their overall troop trees. They have decent armor and decent weaponry with no obvious weaknesses. They are the most common to find.

For Forest Bandits: Followers/Initiates: Arzagos and others briefly mention the Old Gods of Calradia. Many have forgotten...others have kept the old ways. Perhaps...you can convince these cultists to join your cause?
The Followers and Initiates of the Old Gods are terrifying in numbers with a line of light to medium infantry with a variety of one handed, two handed, cutting spears, and ranged weapons. However, they do not have the best armor nor the best armaments but they do have a lot (and I say A LOT) of knives to throw. They have access to no cavalry but use Falxes and Rhomphalias.

For Mountain Bandits: Cave Dwellers/Hill Women: The many cave entrances in the mountains lead to deep passages and caverns, housing communities of all sorts. Some are those who do not enjoy the city life...others are running from the authorities of said cities...while others gather power to invade the glens and the lowlands once more. Will you tame these wild Mountain people?
Strength and height (they are quite tall) is their main attribute, and they possess a large amount of two-handed weaponry, crossbows, and some decent shock cavalry. That being said, they are decent against cavalry charges and for flanking maneuvers. Medium-Heavy infantry is their specialty overall though.

For Sea Raiders: Dishonored/Exiles: Those who came with the first boats from the north were not all settlers and conquerors. Some were prisoners and criminals exiled from their homeland, hoping to make a living for themselves in Calradia. Will you bring them honor once more and make them heroes among Man?
Like the Mountain Bandits, they have a very strong line of heavy infantry with round shields as well as a very good line of heavy cavalry and crossbows. They do not have access to bows outside of the crossbow for ground units, but they are formidable melee fighters in their own right. Their cavalry does come equipped with bows on some units which allows for some skirmishing on mount but do not expect them to outrun any Khuzaits as they are still considered medium/heavy cavalry.

For Steppe Bandits: Nachaghan Remnants/Nachaghan Runaways: When the Great Danger of the East threatened the Steppe Tribes hundreds of years ago, they formed the Khuzait Khanate and banded together against that danger. However...one tribe has mysteriously gone missing in the annals of history - they are Nachaghan. Whether they perished under the foot of the Great Danger or were enveloped into another tribe is a mystery. Some say remnants of the lost tribe still exists...
The Nachaghan are warriors of the steppe and naturally have access to horse units. As they are culturally Khuzait, however, they are not the best armored but their equipment and speed is decent enough. Their melee ground units are average at best with some being equipped with a glaive. Their shields are not the best in the world early but become adequate as they level up. They are the only variant of bandits to have Noble Bows.

For the Desert Bandits: Escaped Servants/Escaped Slaves: Those who were able to flee from a life of slavery turned to the Nahasa Desert for safety. Those who survived long enough have seemingly trained themselves in martial arts not belonging to the Aserai but something more ancient...
The Nahasa people love to throw javelins and form spearwalls while also using two handed axes on occasion. They have access to decent light and medium cavalry equipped with lances, javelins, and swords as well as decent skirmishing mounted javelin throwers. Again, armor is somewhat an issue in terms of survivability, but they make for a decent vanguard. Many of their units use as many as two stacks of Jereed.

QOL: If you want to change the bandit unit sizes, go into the module data folder and edit the banditvariety_parties file. Either change the minimum amount, for how many minimum will show in a party at one time, and the maximum for how many they will have maximum for a specific unit. Keep in mind that only the top three in the list will show in standard bandit parties.

(It is most likely unsafe to remove this mod from your campaign once you start using it, considering the units it adds in and if parties are using said units on the map or in your own party.)
Remember to always back your save as well.
And lastly, have fun!

Furthermore I highly recommend you try out the mod Fourberie by Spinozart1. (https://www.nexusmods.com/mountandblade2bannerlord/mods/2969) His mod adds so many features involving the roguery tree and has adapted my mod to work alongside his. You can hire units over in hideouts up to tier 3. Go over to his mod page for more details!