Enhance the followers added by the excellent mod Khajiit Will Follow.

Basic changes: Each follower now gain the perks perkskillboost (the perk that makes most enchantments unrelated to health, magicka or stamina (like fortify One-Handed, Fortify Illusion, etc...) applied on actors works) and alchemyskillboost (same, but for alchemical effects). Additionnally, they will also gain some vanilla weapon perks (Hack And Slash, Bladesman, etc...) so that if you use a perk overhaul that modify those perks, the changes will carry over to these followers. Which perks they get and at which rank depends on their fighting style (Bikhai, as an accomplished warrior, gain all one-handed and two-handed perks at rank two; Ma'kara and Sariq, both light-armored fighters, gain all one-handed perks at rank two, and Nanak, whose "arm might fall off wielding anything more than a dagger", only have the tier 1 Bladesman Perk

Each Follower also gain some new perks and abilities that reflect their personnality: The following changes are below: 

Bikhai:

Iron Will: Bikhai's resolve reduces all incoming physical damages and stagger by 50% when power-attacking or holding a drawn bow

Stand Together: Bikhai is well aware that warriors that stick together can cover each other's back from a sneaky dagger. When you or another KWF follower is within 20 feets of Bikhai while in combat, they gain 50 points of armor and 10% increased physical damages, and Bikhai gain an equivalent bonus for each affected follower, possibly culminating in 200 points of armor and 40% increased physical damages

Heavy Armor Mastery: Sure, It might pinches in uncomfortable places at the worst moment, but there's no denying heavy armor is far from useless against mighty foes, as Bikhai came to learn. When he wears heavy gauntlets, boots and cuirass, and have no light armor equipped, Bikhai takes 25% less damages and stagger from power-attacks

Nanak:

In addition to the following perks, I also gave him the "stoneflesh" spell and the rank 2 of the "Mage Armor" perk, so he still has some kind of physical protection, and altered his class so he no longer gain levels in light or heavy armor, instead gaining level in restoration and alteration.

Mage's regalia; Nanak spent years devoted to reading every book in the bard's college or the Arcaneum in search of all kind of magic knowledge. this devotion  left him with a great Arcane potential, but a rather laughable ignorance of how to best wear armor of any kind. As such, he's at his strongest when wearing comfy robes, gaining 50% increased magicka regeneration, 35% magic resistance, 30% increased spells magnitude or duration(depending on the spell's school) and reduces incoming physical damages by 25% while he's casting or concentrating on a spell. If Nanak is wearing any piece of light or heavy armor, all these effects are nullified.

Fortitude: Nanak's Stubborn nature leaves all spells targeting him, whether friendly or hostiles,15% less powerful

Channeler: Wielding a staff improves spells magnitude or duration by 25%. Additionally, when wielding a staff, Nanak drains enchantment charges half as fast and slowly regenerate them.

Ma'Kara:

Resilience: While crossing all across skyrim searching for her brother, encountering bandits that nearly killed her in the process and left her with broken ribs, Ma'kara discovered within herself an unexpected resistance to physical pain. As her health decline, she gain increased resistance against physical attacks (up to 40% reduced damages when below 25% health) and increased critical hit chances and damages (respectively up to 40% increased chances and 80% increased critical damages when below 25% health). 

Wellspring Of Life: . Upon receiving a healing spell or effect, Ma'Kara will gain 150 points of armor and 30% magic resistance and increased physical damage for 20 seconds.

Light Armor Mastery: Light armor is perfect to cross the battlefield quickly, and provide padding against hostile magic. When Ma'Kara wears light gauntlets, boots, and cuirass, and have no heavy armor equipped, she gain 15% increased magic resistance.

Sariq:

Opportunist: As any good thief, assassin or cutthroat knows, honor is a fool's virtue, and Sariq pride himself on being an excellent thief: As such, he gain 20% increased physical damages, 40% increased critical damages, and 20% more chance of critical hit against weakened targets*

*Are considered as weakened any target meeting at least one of the following criteria:
-Is affected by an alchemical poison (poison applied via spells or enemy poisoned blades won't work, you'll have to poison the target yourself if you
want to weaken it for Sariq)
-is effecting a power attack or fully drawing a bow
-is staggered
-is turning their back on Sariq
-Has below 40% of their maximum health

Mithridatism: As a lifelong thief, Sariq received his share of stab wounds, poisoning or even spell-burnt scars from both rivals thieves and angered targets. As such his body began to slowly accomodate to them. Sariq gain 50% increased poison and disease resistance. Additionally, whenever he's hit by an elemental spell, he'll gain 25% resistance to the spell's element, and if staggered, will gain 75 points of armor. Only one of each aforementioned effect can take place at a time, and, if not dispelled by another effect, will last for 10 seconds.

Light Armor Mastery: Same as Ma'Kara